Fecal occult blood testing: preparation for analysis. What can you eat for reliable results? How to pass and what shows the analysis of feces for occult blood

Particular attention is required to prepare for the analysis of feces for occult blood, since in its absence or improper conduct, false positive results can be obtained.

• regular diarrhea;
• unexplained weight loss.

Types of tests

• immunochemical test.

1. Enema is prohibited.

• potato;
• bread;

Collection of feces for research

False results

Diet before occult blood test

Indications for an occult blood test

The indications for an occult blood test are:

· stomach ulcer;

· nonspecific ulcerative colitis;

The patient is put on a three-day diet before an occult blood test. She excludes fish and meat, liver, green vegetables, white beans, spinach, pomegranates, apples, bell peppers, beets, horseradish, tomatoes and blueberries from the diet. However, the diet before testing for occult blood includes potatoes, cereals, dairy products, boiled eggs, butter, bread, and a small amount of fresh fruit.

Before donating feces for occult blood, the diet excludes not only the consumption of certain foods, but also the use of medications containing iron. These drugs include: bismuth and barium sulfate. They can change the color of the stool.

Also, before donating feces for occult blood, the diet, in addition to restrictions in certain foods, prohibits the use of laxatives, rectal suppositories and drugs that affect intestinal motility.

Two days before the analysis, it is undesirable to brush your teeth with a toothbrush, as this can damage the gums and blood from the oral cavity will enter the stomach.

Women during menstruation do not take an occult blood test.

It is impossible to put an enema on the eve of the test, as it can damage the mucous membrane and lead to incorrect results.

The admixture of urine to feces is unacceptable.

Following a diet before an occult blood test and following all of the above recommendations can ensure accurate test results.

Fecal occult blood test procedure

The collection of material for analysis occurs in the same way as in the general analysis of feces. As a container, use a glass or plastic container, or a special container.

Fecal sampling is carried out from four places of fresh feces, eliminating the ingress of urine into them. For the most reliable results, the stool should be delivered to the laboratory within three hours of a bowel movement.

More precise recommendations that are important for the diagnosis of a particular disease can be given by the attending physician. A similar analysis can be taken at a medical institution at the place of residence. In addition, you can take a fecal occult blood test at numerous medical centers and private laboratories at any convenient time. Test results will be ready within six days. The normal value of the result of a fecal occult blood test is negative.

Can the test result be false?

It happens that the analysis gives a false result. Most often, when the occult blood diet is not followed, or there is bleeding localized in the gums, a false positive test result is observed. Thus, strict observance of the occult blood diet is a prerequisite before taking the sample.

False negative test results are also possible. This happens in cases where the bleeding is not constant, but is periodically renewed.

In general, the sample is quite reliable, but tests must be taken twice to confirm the results. If all the conditions are met before donating feces for occult blood, the diet is observed, samples are taken at intervals of 3-4 days, and the result of the studies turned out to be the same, then it is reliable.

Positive test result

When the occult blood diet is followed, all the conditions for preparing for the test are met, and the result of the analysis gave a positive result - this may indicate ulcerative, oncological or inflammatory processes. A positive test is a serious reason for the diagnosis. If the doctor has written out a referral for an occult blood test, the diet must be strictly followed before taking it.

For timely diagnosis and in order to avoid aggravation of the course of the disease, the test must be passed at the first request in compliance with the prescribed preparation. The sooner a correct diagnosis is made, the sooner effective treatment can be prescribed.

Quantitative immunochemical test

To date, there is a relatively new method for determining occult blood - a quantitative immunochemical test. It is used in the diagnosis of colorectal cancer. Preparation for the test is minimal. To determine occult blood, you just need to take a stool test, and there is no need to follow a diet.

Diet is not needed for the reason that this study uses antibodies to hemoglobin. Such antibodies do not react to myoglobin contained in the eaten meat of animals. The test is specific, characterized by high sensitivity and accuracy. The absence of the need to follow a diet makes this method very convenient for patients.

An occult blood test makes it possible to diagnose a number of diseases even before they cause irreparable harm to the body.

If your stomach hurts persistently and does not stop longer than usual - do not delay and go to the hospital, you may need to do a fecal occult blood test! It is necessary to determine the causes of pain as early as possible in order to avoid any complications and the possible development of diseases of the gastrointestinal tract, genitourinary system.

It is also possible that after a bowel movement you notice the presence of blood in the stool.

When is a fecal occult blood test ordered?

At the doctor's appointment, an examination of the abdominal cavity and the internal organs located in it will be performed. After examination, the doctor, having made certain conclusions, may prescribe further diagnostics. Fecal occult blood testing is an important procedure for establishing an accurate diagnosis.

This analysis is prescribed if the doctor suspects bleeding in one of the sections of the digestive tract. The analysis is assigned if the following factors take place:

• prolonged abdominal pain, nausea, heartburn, vomiting;
• with constant loose stools, false urge to empty, lack of appetite and weight loss, fever;
• in case of detection of tumors in the gastrointestinal tract;
• in case of detection of worms;
• if you have previously had a stomach ulcer.

With heavy bleeding in any part of the gastrointestinal tract, the blood changes the appearance of the feces quite strongly, which becomes noticeable to the naked eye. If bleeding occurs in the upper sections, the stool becomes black, similar to tar due to the interaction of blood with local enzymes.

What is research for?

If there is suspicion of bleeding in any of the sections of the gastrointestinal tract, doctors immediately prescribe tests for the patient to give feces.

Quite often, bleeding can be determined visually by the presence of blood in vomit or feces. In this case, immediate action should be taken. It is worth noting that this may not always indicate internal bleeding. A similar effect can give nosebleeds, bleeding gums.

In most cases, internal bleeding in the organs of the gastrointestinal tract can be intermittent and not abundant, traces of it will not be noticeable in the feces. If your doctor suspects it, he will order a fecal occult blood test for you.

This analysis is designed to detect changes in hemoglobin in red blood cells. The study is effective even when the bleeding is so weak that red blood cells are simply not visible under a microscope.

Changes in hemoglobin are detected by the interaction of the studied feces and special chemicals (reagents), which change their color as a result of the reaction.

Sometimes an enzyme immunoassay of the material (feces) is performed to detect occult blood.

The analysis of feces for occult blood allows you to:

• to diagnose the presence and degree of development of diseases of the gastrointestinal tract
• determine the nature and extent of damage to the mucous membrane of the tract.

Preparation for analysis

If a patient has been assigned a fecal occult blood test, he needs to follow certain guidelines.

It is necessary to start preparing for an occult blood test not two days in advance, but at least a week in advance.

Aspirin, non-steroidal anti-inflammatory drugs, and other analgesics should be stopped approximately ten days before stool collection. It is worth stopping taking various laxatives and drugs, which include bismuth and iron.

It is important to note that if the patient was assigned diagnostics using x-rays, then the collection of feces should be carried out at least two to three days after the x-ray.

What can you eat before the analysis.

Before taking an occult blood test, following a special diet is a very important procedure, the implementation of which directly affects the accuracy and reliability of its result. Maintaining the right balance of fats, proteins and carbohydrates in food will help to get the right conclusion.

According to Schmidt, it involves the use of dairy products.

How many days is done?

Preparation for analysis can take about a week. This is exactly the time that the patient needs to follow all the necessary instructions to obtain the most accurate results of the fecal occult blood test. Therefore, it is necessary to approach this issue as responsibly as possible, since this is in the interests of the patient himself.

How to properly assemble a chair?

The collection of the material necessary for analysis - feces must be carried out in compliance with certain nuances. This also affects the quality of the analysis result.

Most importantly, bowel movements should be spontaneous. It is contraindicated to push and make efforts to speed up the emptying process. Moreover, the use of laxatives in any form, both medicinal and folk, is contraindicated.

It is important to consider here that feces are collected from various parts of the feces. Do not allow mixing of urine and feces.

If possible, the collected feces should be delivered to the laboratory for analysis no later than three hours later. It should be stored in the refrigerator at a temperature of four to six degrees.

Analysis results

After the stool is collected, the patient takes it to the laboratory for testing for occult bleeding. The results of the analysis can be ready the very next day.

The result of the obtained analysis of feces for occult bleeding determines all further actions, both for the patient and the doctor.

A negative test result is considered normal. This means that there is no bleeding in the gastrointestinal tract. It shows that the stool contains substances that the stomach is not able to digest.

The problem with fecal occult bleeding analysis is that it cannot always show the presence of polyps in the intestine. If the doctor has suspicions about this, he may prescribe additional diagnostics.

A positive result means that bleeding in the gastrointestinal tract is present. The reasons for this result may be:

1. intestinal tuberculosis;
2. stomach ulcer;
3. duodenal ulcer;
4. oncology of the intestines, stomach, esophagus;
5. nonspecific ulcerative colitis;
6. haemorrhoids;
7. worms (can scratch the walls of the intestine);
8. colorectal cancer;
9. erosive esophagitis (inflammation of the esophagus that affects its mucous membrane).

It should be borne in mind that the result of a fecal occult blood test may turn out to be false positive. The reasons for this can be nose and dental bleeding. In women, the presence of blood in the feces can be caused by radiation after oncological diseases of the genital organs, vaginal varicose veins in the last days of pregnancy.

Quite often, the result of this survey is false positive due to non-compliance with the rules and instructions for its preparation.

Where is the best place to do the analysis?

In most cases, a fecal occult blood test is ordered directly by the attending physician. Therefore, it is done in the clinic in which the patient is registered. The analysis can be taken at various medical centers. For the convenience of the patient, a blood test for occult bleeding can be done in a specialized laboratory at any time convenient for him. Many people take several tests at the same time to different laboratories to obtain a more accurate and reliable result.

The price for the analysis varies depending on the medical institution where you do it. The delivery of the analysis in the clinic at the place of registration is absolutely free.

You will only have to spend money on a plastic container for collecting biological material. Analyzes in medical centers and laboratories are paid. On average, the price is about 130 hryvnia in Ukraine and rubles in Russia.

Reviews

Nikolay, 33 years old.

I suffered for a long time with the intestines. Passed feces for occult blood. It turned out that I had intestinal tuberculosis. I'm on the mend now, but at least I know what it's for.

I had a whole story with this survey. I did it several times, and several times - positive. Then only it turned out that during menstruation it is contraindicated to donate feces for blood.

Feces for occult blood: preparation, diet, interpretation of the results

In order to determine the state of the human body, you need to undergo an examination and pass some materials to the laboratory for research. There are a large number of varieties of tests, one of them is feces for occult blood. Preparation takes several days.

Collection of feces for occult blood: indications

The analysis is needed in order to determine whether there is damage to the organs of the gastrointestinal tract. If the integrity of the mucous membrane of at least one organ is broken, this will be seen from the results.

Reasons for analysis may include:

• severe bowel disease;
• Ulcer;
• Colitis;
• polyps;
• Anemia;
• poor appetite;
• abnormal stool;
• A sharp change in weight in the direction of decrease;
• Frequent constipation;
• Heartburn;
• Acute pain in the abdomen;
• Constant nausea.

In addition, feces for occult blood are taken if there is a suspicion of an oncological disease or a benign neoplasm.

You can take a referral for analysis from a surgeon, therapist, oncologist or gastroenterologist.

What do you need to know about the study?

At the present stage, everyone who is being tested for occult blood needs to have at least general information about this.

The fresher the sample, the more accurate the results will be.

Before taking the samples, you need a simple preparation for a few days.

The daily amount of dense excrement is approximately 200 grams. Significantly more comes out with pathological processes of the gastrointestinal tract, less - with malnutrition, the use of protein foods, and problems with defecation.

By the form, you can understand whether there are deviations in the work of the intestines. In a healthy person, the stool has a sausage-shaped form of medium density, brown. When disturbed, the feces can be very dense or liquid, lumps or in the form of a ribbon. In severe pathologies, not only the appearance changes, but also the composition, smell, various impurities appear.

In normal feces, there may be particles of undigested food - the norm is the peel of fruits or vegetables, cartilage or tendons.

If mucus or blood is visible to the naked eye, this indicates a disease of the colon.

Almost all patients know how the medical staff should behave. However, few people remember that there are also general recommendations for patients regarding the delivery of any analysis, including feces. They are as follows.

Feces are collected after a natural bowel movement. Do not use enemas or laxatives. It is not recommended to use it a few hours before collecting the sample, and special preparations for another 3-4 days. If you violate this rule, the analysis will not be accurate. However, this applies only when feces are donated for occult blood.

The accuracy of the results depends on the freshness of the material. The ideal option is if the sample reaches the laboratory within 3-6.5 hours after its collection. This rule is not always easy to follow, however, some microorganisms live outside for only a few hours. Therefore, getting a complete picture over time becomes more and more difficult. It is desirable to hand over the analysis till 10 o'clock.

3-4 days before sampling, special preparation is needed - diet. You can not eat a lot and those foods that cause discomfort in the stomach and intestines. Avoid foods that stain feces, such as beets, greens, and certain fruits.

If possible, do not take pharmaceutical preparations for a week before sampling. The exception is those that are taken regularly for chronic diseases. This is due to the fact that some drugs stain the feces in a different color or change the composition of the microflora. In addition, do not conduct additional bowel examinations using special enemas, such as barium. It discolors feces and changes their structure.

Collect the sample in a special jar-container with a spoon, you need to purchase it in advance. To make an accurate analysis, a few grams of the material is enough.

The last rule concerns women. During menstruation, sampling is not recommended, as blood can get into the excrement and ruin the results.

Diet before fecal occult blood test

A few days before sampling, a special diet is prescribed, which must be followed in order for the analysis to be correct the first time.

During this period, you can not eat:

• Liver in any form;
• legumes;
• Fish and meat dishes;
• Apples and other fruits that affect the color of feces;
• Greens, in particular spinach;
• Some vegetables: tomatoes, sweet peppers, beets, spicy horseradish.

Sample menu for one day:

• Bread and butter, milk soup, a few pears or peaches, canned in winter;
• Mashed potatoes, 2 boiled eggs, milk jelly;
• Yogurt without dye;
• A glass of kefir or fruit.

The amount of food taken at one time should not exceed grams. The same set of products with some correction and variations should be eaten for another 2 days.

Feces for occult blood: decoding

Ready analysis, interpretation, is called a coprogram. First of all, the presence of blood, even in the form of individual cells, is not characteristic of feces. Therefore, a microscopic examination is carried out to find out if red blood cells are present in the excrement?

They can be there for several reasons: damage to the stomach and small intestine or lower part, that is, the rectum, colon and anus. If the bleeding is heavy, the discharge is already noticeable - the feces will be black, in case of minor damage, it is difficult to determine anything without special studies.

Damage to the lower digestive system is noticeable due to the presence of bright red impurities. Since some products and drugs can have a similar effect, you need to undergo a diagnosis, that is, donate feces.

This analysis will show if there are problems in the upper part of the food system, in the case of the presence of red blood cells in the material provided for the study. There are no special norms for this, even the smallest content of blood particles in the feces is enough.

If the gums or nasal mucosa bleed, the analysis will be positive. Therefore, careful preparation for the procedure is needed, and it is not recommended to brush your teeth the day before and try to avoid various injuries.

Fecal occult blood test: preparation, price

A fecal occult blood test can detect traces of blood that are not visible on microscopic examination.

An occult blood test can detect bleeding from any part of the gastrointestinal tract.

Indications for analysis: suspicion of the presence of bleeding in any part of the gastrointestinal tract.

Preparing for a fecal occult blood test

A few days (about a week) before the stool test, you must stop taking medicines (especially iron, bismuth, laxatives).

On the eve of the analysis, you can not put an enema.

After an x-ray examination of the intestines and stomach, it is not recommended to prescribe stool tests earlier than two days later.

Required diet before taking a fecal occult blood test

Three days before the fecal analysis should be excluded from the usual diet:

• liver;
• meat;
• foods that contain iron (green onions, white beans, spinach, bell peppers, apples).

For the correct delivery of a fecal occult blood test, you should empty your intestines yourself into a plastic, disposable, sealed container with a tightly screwed lid.

Urine must not be mixed with feces.

Before sending the analysis to the laboratory, the prepared material must be kept in a refrigerator at an average temperature of about 5 degrees Celsius. The stool container should be delivered to the diagnostic laboratory on the same day that the material was collected.

Fecal analysis is prepared for six full working days.

The normal value of a fecal occult blood test is negative.

Determination of occult blood in feces

Immunochromatography is used to determine occult blood in the feces.

Its completion time is one day.

The method of immunochromatography is prescribed to patients to determine human intact transferrin and hemoglobin in order to detect hidden intestinal bleeding.

Immunography is prescribed to patients for:

• diagnosis and detection of diseases of the duodenum and stomach;
• Crohn's disease;
• neoplasms of the large intestine (polyps, cancer).

• sensitivity and specificity of the test - more than 99%;
• lack of cross-reactions with transferrin and hemoglobin of animal origin (meat can not be excluded from the daily diet);
• in addition to identifying latent intestinal bleeding, it is possible to clarify damage to the gastrointestinal tract (lower and upper sections).

It is not allowed to take a stool test for hidden bleeding:

• after strong straining during defecation;
• hematuria;
• bleeding with hemorrhoids;
• menses.

In Moscow, the cost of fecal occult blood tests is 300 (three hundred) rubles.

Fecal occult blood test

Causes of blood in the stool

The main and most common cause of occult blood in the feces is tumor processes in the intestines (colorectal cancer). Occult blood in the stool is the one that is not visible visually and even under a microscope. It is known that intestinal tumors bleed. This blood in the initial stages of the disease is an insignificant amount. Once in the intestinal lumen, erythrocytes and, together with them, hemoglobin are destroyed by the action of digestive enzymes, therefore they become invisible.

In addition to colorectal cancer, the causes of occult blood in the stool in an adult can be polyps in the intestines, any inflammatory process, ulcerative process in the intestines, diverticulosis (pockets in the intestines), Crohn's disease, ulcerative colitis (UC).

What is research for?

The analysis of feces for occult blood shows the presence of precisely invisible hemoglobin and red blood cells. The study is very valuable in determining intestinal bleeding in the early stages, when it is not yet visible to the eye. When is a fecal occult blood test indicated? Below are the main factors:

• Pain or discomfort during or before a bowel movement.
• Any impurities in the feces (mucus, foam).
• Changes in the character of the stool. It became liquid or vice versa too dense.
• There are occasional traces of blood in the stool.
• Decreased appetite or significant weight loss.
• Pain in the abdomen of any localization.
• The presence of symptoms such as heartburn, nausea, vomiting, iron taste in the mouth.
• Periodic unreasonable increase in body temperature.
• Annually as a screening examination of patients over 40 years of age. It is carried out for the early detection of tumors of the large intestine.

In the presence of any of the above symptoms, it is recommended to donate feces for an occult blood test.

Preparation for the analysis of feces for occult blood, what is needed?

Patient preparation is necessary only in the case of analysis by chemical reactions (benzidine, guaiac samples). These tests often give false-positive reactions, for example, to animal-derived hemoglobin found in meat foods, or to chemicals in foods and vitamins.

It should be borne in mind that the analysis is reliable only for bleeding from the lower intestine (colon and rectum). In the upper sections, hemoglobin is significantly affected by digestive enzymes and is destroyed. Therefore, after the study, with a positive result, it is recommended to undergo an additional examination (colonoscopy, for example).

How to prepare for the analysis?

1. Diet before fecal occult blood test. For three days (72 hours), food of animal origin (meat, fish) should be excluded from the diet. You should also exclude some vegetables, especially green ones: cauliflower, cucumber, horseradish, green apples, spinach, lettuce, any greens and zucchini. Tomatoes are also excluded.
2. The use of iron-containing drugs, bismuth and barium sulfate is not recommended. Also, on the eve of the study, you can not take acetysalicylic acid (aspirin) and ascorbic acid (vitamin C).
3. Three days before the study, it is not recommended to carry out any diagnostic or therapeutic manipulations with the intestines (X-ray contrast examination, sigmoidoscopy, colonoscopy).
4. Do not use laxatives and do not give enemas. The material for analysis is collected after three spontaneous bowel movements from different parts of the stool.
5. Women during menstruation are not recommended to conduct this analysis.

How to pass the analysis?

For a reliable result, after proper preparation, you need to collect feces in a specially designed container purchased at a pharmacy. The material should be taken after natural emptying from several areas of stool. The amount of material is sufficient in the amount of 1 teaspoon.

Deciphering the results of the analysis

A positive reaction of the analysis indicates the processes in the intestine, leading to a violation of the integrity of its mucous membrane. This means that red blood cells and hemoglobin enter the intestinal lumen. But do not rely only on the results of one analysis. A number of diseases of the intestines and other organs can give a positive reaction. For example, nosebleeds, stomach polyps, esophageal ulcers, hemorrhoids, and even helminths. To make an accurate diagnosis, a complete examination of the patient is necessary.

The result of the analysis may also turn out to be false positive if there was a reaction not to human hemoglobin, but to substances or dyes contained in food. This occurs, as a rule, with improper or insufficient preparation of the patient for the study. In any case, a positive result is a reason for a deeper examination of the patient.

A negative test result is the norm for a person. But such a result does not always indicate the absence of intestinal bleeding and should not reassure either the patient or the doctor. A negative result is of no diagnostic value. For greater reliability with a negative result, the analysis can be repeated three times.

If you are concerned:

• stomach pain, nausea or vomiting;
• heartburn;
• stool disorders, alternating constipation;
• mood swings;

Preparation for the analysis of feces for occult blood: diet before donation, how to donate

The study of feces for occult blood is one of the laboratory tests that makes it possible to diagnose internal bleeding in one of the sections of the gastrointestinal tract with a high degree of probability. Particular attention is required to prepare for the analysis of feces for occult blood, since in its absence or improper conduct, false positive results can be obtained.

Indications for the purpose of the analysis

A study of feces for hidden blood in it is prescribed for the following patient complaints:

• persistent / intermittent abdominal pain;
• frequent symptoms of dyspeptic disorder - nausea, vomiting, heartburn;
• regular diarrhea;
• unexplained weight loss.

Testing of feces for the blood present in their composition is prescribed to confirm the diagnosis, for example, peptic ulcer or erosive gastritis. The overall goal of the analysis is to identify hidden damage to the mucous membranes of the stomach or intestinal tract.

Types of tests

In the presence of bleeding areas of the mucosa, blood may be present in human excrement. If the place of the opened bleeding is the stomach or duodenum, then the feces get a dark red color. When the surface of the large intestine is damaged, they become scarlet. But it is not always possible to see blood impurities in a person's stool. Very often, small ulcers bleed only intermittently.

Research is carried out in two ways:

• Gregersen's method (benzidine test);
• immunochemical test.

The Gregersen test is quite informative, but only if the patient conducts thorough preparation.

The Gregersen technique makes it possible to detect even the minimum concentration of hemoglobin. This is both an advantage and a disadvantage of the method. Benzodine colors iron molecules blue, but it reacts to both human and extraneous hemoglobin (present in meat).

The immunochemical method is more accurate. Its main drawback is that it is rather long in time. Test results will be received only two weeks after the submission of the material for research. Therefore, in most cases, the delivery of feces for analysis according to the Gregersen method is prescribed.

Preparation for the delivery of the analysis according to Gregersen

To get the most reliable results, it is necessary to properly prepare for the delivery of feces. Recommendations will be as follows:

1. A week before the planned delivery, it is necessary to stop taking drugs such as laxatives, bismuth- and iron-containing, anti-inflammatory nonsteroidal drugs. It is forbidden to use acetylsalicylic acid and medicines containing it.
2. It is necessary to refuse the introduction of rectal suppositories.
3. Enema is prohibited.
4. Before analyzing feces for occult blood - two days before delivery - any instrumental tests of the gastrointestinal tract should be excluded. During the study, the mucosa may be accidentally damaged. Excessive blood may cause false positive results.
5. A few days before the collection of excrement, you should stop brushing your teeth. Even a small amount of blood released when the gums are damaged can enter the stomach. And this hemoglobin can also negatively affect the final result.

The main point of preparation for passing the analysis is strict adherence to the diet

The patient's diet should completely exclude foods high in iron. The collection of feces must be preceded by a refusal:

Ideally, in order not to make a mistake with the menu, doctors recommend sticking to a milk diet on the days of preparing for the delivery of feces. The diet may also include:

• potato;
• bread;
• cereals (exception - buckwheat, oatmeal, cells, lentils, peas).

Collection of feces for research

Even carefully conducted preparation will be completely useless if the biological material is collected incorrectly.

There are special containers for transporting feces to the laboratory - they are sterile and guarantee the biological purity of the collected excrement

How to donate feces correctly? To obtain material suitable for research, the following recommendations must be observed:

1. A sterile container must be used to collect excreta. It can be purchased at any pharmacy. The set includes a jar with a lid and a special spoon.
2. First you need to empty the bladder. Then lay an oilcloth in the toilet.
3. After emptying the bowels, it is necessary to take a collection of three servings of feces from different places.

The material must be delivered to the laboratory within the next three hours. It is not subject to storage.

False results

Failure to follow the rules of preparation before donating feces can cause erroneous results. They can be either false positives or false negatives.

The main reason for false positive tests indicating the presence of internal bleeding is improper preparation.

False positive results are quite common. The reason is the negligent attitude of a person to the preparatory stage. In this case, the test shows a high hemoglobin content in the absence of internal bleeding. Only one apple eaten a day before the delivery of biological material can distort the final results.

Properly carried out preparation for the study of feces for occult blood in many cases allows you to avoid a very unpleasant colonoscopy procedure. The technique is an examination of the intestine by introducing equipment through the anus.

ATTENTION! All information on the site is for informational purposes only and does not claim to be absolutely accurate from a medical point of view. Treatment must be carried out by a qualified doctor. By self-medicating, you can harm yourself!

To date, there are many ways to diagnose the body and study various biomaterials. To diagnose the internal organs and the condition of the gastrointestinal tract, feces are taken for occult blood. Preparation for such an analysis is simply necessary, because due to improper nutrition, the result can be distorted.

Blood in the stool is a sign of gastrointestinal pathology

For the normal functioning of all internal organs, it is necessary from time to time to diagnose and take an analysis in order to be able to determine the disease at an early stage. The state of internal organs cannot be examined in any way without resorting to special equipment and analysis methods.

An analysis of feces for the detection of occult blood in the body shows the presence or absence of internal bleeding of the gastrointestinal tract. Diagnosis can show the development of many diseases associated with disruption of the digestive system. Blood occurs in wounds, ulcers and microcracks. When diagnosing with the help of visual equipment, such damage is not visible, because of this, there is a need for fecal analysis.

In a normal state of health, no more than 2 ml of blood is excreted daily with feces.

This is considered the norm. If it is more, this fact indicates internal bleeding, which may be evidence of many diseases - colitis, ulcers, tumors and other pathologies of the gastrointestinal tract.

An analysis for the detection of occult blood in the feces is prescribed by a doctor in the following cases:

• suspected ulcerative colitis
• colorectal cancer diagnosis
• anemia (anemia)
• diagnosis of intestinal bleeding
• preventive diagnostics for people over 50

When the doctor writes out a referral, he conducts a consultation on how to properly prepare for an occult blood test.

Abundant internal bleeding is visible to the naked eye. They change the color and texture of stool. Color specialists can determine which organ is affected. Bloody patches of bright color indicate problems in the colon or rectum. If the stool becomes almost black in color, this is a sign of problems in the stomach or esophagus.

Preparation for analysis

Feces for analysis must be collected in a special sterile container!

In order for the analysis result to be as accurate as possible, it is necessary to properly prepare for the analysis. First of all, a few days before the delivery, you must follow a special diet. It is necessary to completely eradicate meat and fish, vitamin complex and medicines, alcohol, seafood from the diet.

The analysis is carried out in several ways. The most common is the benzidine test (Gregersen's reaction). It gives a reaction not only to human hemoglobin, but also to proteins of animal origin, therefore, eating meat dishes on the eve of tests, there may be false data.

Diagnosis using the immunochemical method does not require a special diet, but still meat and fish should be abandoned a few days before the tests. It is also necessary to abandon drugs that have anti-inflammatory and analgesic effects. They usually contain ibuprofen, acetylsalicylic acid, drugs containing iron. Also, the stool should be natural, without the help of an enema or laxatives. Otherwise, the admixture of medicinal substances can provoke an incorrect result.

For more information about the analysis of feces for occult blood, see the video:

Very carefully you need to donate feces to women during menstruation. If blood enters the stool, the result will be false. When it is necessary to take a stool sample from an inpatient, this is warned in advance to exclude the use of suppositories, enemas, petroleum jelly and other drugs.

The result of the analysis can be positive or negative.

A positive result means that the stool contains more blood than expected. This indicates one or more diseases:

1. stomach ulcer, inflammation of the duodenum
2. infections caused by Koch's wand
3. ulcerative colitis
4. stomach cancer
5. thrombophlebitis and esophageal varices
6. stomatitis, periodontal disease, periodontitis, gum bleeding
7. nasopharyngeal bleeding

In addition to diseases of the gastrointestinal tract, diseases of the nose or throat can be the cause of latent blood in the feces. Bleeding gums, dilated vessels, and nosebleeds are also causes of occult blood. Hemorrhoids and anal fissures are a common cause of blood in the stool.

With a positive result, it is imperative to prescribe a second diagnosis, because the possibility of a false result associated with improper preparation for the delivery of feces is not ruled out.

In addition to the analysis of feces for occult blood, other diagnostic methods are also carried out to identify a particular disease.

In the end, it is important to note that it is necessary to take tests at least once a year, for the purpose of prevention. Internal bleeding may not show symptoms, not disturb a person for a long time, although the disease develops. An analysis for occult blood in the feces allows you to identify many pathologies and provide timely assistance. As a rule, the blood rate increases with vascular diseases (blood clots, varicose veins) or the gastrointestinal tract (ulcers, colitis, cancer, etc.) for reliability, it is recommended to repeat the analysis after a while, since the possibility of false data is not ruled out.

How to pass and what does a fecal occult blood test show?

Blood during bowel movements can indicate a serious illness, ranging from an anal fissure to a malignant neoplasm in the digestive organs.

However, in the early stages, the pathology often develops without obvious symptoms, and it can be difficult to notice hidden bleeding.

A fecal occult blood test detects the smallest impurities of blood and allows you to diagnose diseases in the initial phases, which is extremely important when oncology is suspected.

In what cases are they prescribed?

A fecal occult blood test is prescribed for the following symptoms:

• Stomach ache;
• Dyspeptic manifestations (heartburn, bloating, nausea) for a long time;
• Frequent diarrhoea, constantly liquefied stool constitution;
• Other digestive disorders;
• Sudden weight loss for no apparent reason;
• Clinical analysis of feces does not show the presence of bleeding.

The presence of occult blood must be checked for suspected inflammation of the digestive tract, peptic ulcer, neoplasms.

The indications for this test are quite serious, and if the doctor suggests doing a stool test, you should not ignore his recommendations. Unlike many other methods of examining the gastrointestinal tract, the test is completely safe and painless.

Research methods

Modern laboratories use 2 main methods of analysis:

1. The Gregersen reaction, as the chemical fecal occult blood test is called, is used to detect bleeding in all parts of the gastrointestinal tract. The test is sensitive to both human and animal hemoglobin, so special preparation and a meat-free diet are required before testing.
2. Analysis of feces for occult blood by the immunochemical method is prescribed for the diagnosis of pathologies of the lower part of the digestive tract. The study only responds to human hemoglobin, so patients do not need to limit their diet to meat and iron-rich foods. Fecal occult blood testing without diet is more convenient and is actively used as a screening test for colorectal cancer.

Immunochemical analysis is considered more modern and sensitive, but it is not informative in relation to bleeding in the esophagus and stomach.

The choice of method is carried out by the doctor, depending on the patient's complaints. Before going to the laboratory, consult with a specialist!

How to prepare?

Preparation of the patient depends on the chosen research technique.

The delivery of a fecal occult blood test by the immunochemical method does not require changes in nutrition.

2 weeks before it should be abandoned:

• From drugs that increase the risk of bleeding (aspirin, ibuprofen).
• From laxatives.
• From procedures that can damage the mucous membranes of the gastrointestinal tract (enemas, colonoscopy, etc.).

Preparation for analysis by chemical sampling includes a special diet. The Gregersen reaction can give a false result for digested hemoglobin and myoglobin of meat products, for some vitamins and nutrients.

Diet in the analysis of fecal blood excludes:

The diet should begin 3 to 4 days before the study, in addition, for this period you should:

• Avoid taking drugs, food, drinks that can stain feces and affect intestinal motility;
• Refuse enzymes;
• Do not use rectal suppositories;
• Postpone X-ray examination of the gastrointestinal tract;
• Replace brushing with hygienic rinsing to prevent damage to the gums and blood from the mouth into the esophagus;
• Women do not perform a fecal occult blood test during menstruation and 3 days before and after it.

How to assemble?

Competent preparation and delivery of the analysis affect the reliability of its results.

In no case should foreign impurities enter the test material: water, urine, genital secretions, radiopaque compositions, suppository components, etc.

How to prepare for stool collection:

1. Purchase a sterile container. It is a container with a screw cap and a spoon. Containers are sold in pharmacies and laboratories.
2. Disinfect the vessel, pot, other container suitable for defecation. Wash with soap, rinse several times with clean water, pour over with boiling water. You can't collect feces from the toilet.

• For research, only feces of natural defecation are suitable, without laxatives and enemas.
• Defecate should be in a prepared container, avoiding urine.
• Take feces with a special spoon and transfer the material to a container.
• Close the lid.
• Attach the fecal occult blood test form issued by the laboratory or prescribed by the doctor to the container.

The amount of feces for analysis is not less than a teaspoon and not more than 1/3 of the volume of the container. It is advisable to take not one, but several fragments of feces, so that the detection of occult blood is as effective as possible.

How to submit?

Prepared feces cannot be stored; only fresh material that has not been frozen and preserved is suitable for analysis.

The best option, how to hand over the container, if it is not possible to deliver it to the laboratory immediately, is to put it in the refrigerator at a temperature of + 2 - 8 ° C, transport it in a thermos with an ice cube. The maximum storage time is no more than 3 hours.

The result of a fecal occult blood test is prepared in a few days. Typically, the study period is 3-6 days, depending on how much analysis is done in a particular laboratory.

Analysis results

The rate of blood excretion with the feces of a healthy person is up to 2 mg of hemoglobin per 1 g of material. A positive result means that occult blood is found in the feces, but its source must be further identified.

The intensity of the reaction is expressed by the number of "pluses": from one - weakly positive, to four.

Gregersen's occult blood test may show:

• Erosive gastroduodenitis;
• Exacerbation of an ulcer;
• Tumor in the stomach, intestines;
• Diverticulum;
• Varicose veins of the esophagus;
• Haemorrhoids;
• intestinal tuberculosis;
• Crohn's disease;
• polyps;
• Nonspecific ulcerative colitis.

With the chemical method of research, there may be other causes of latent blood in the analysis of feces that are not associated with diseases of the gastrointestinal tract.

A false-positive result is likely if the diet is violated before giving feces, in the presence of bleeding in the nasopharynx, helminthic invasion, blood diseases, and menstruation. An analysis of feces for occult blood in infants is positive for allergies, lactase deficiency, and constipation.

What the immunochemical method shows: a result > 50 ng / ml indicates hemorrhoids, polyps, colorectal carcinoma, ulcerative colitis or Crohn's disease.

The interpretation of laboratory results should be done by a physician. If the test for occult blood in the feces is positive, additional diagnostic measures should be taken to clarify the pathology.

Where to do?

Having received a referral for research, the patient himself has the right to choose where to donate feces for latent blood: in a public clinic or a private laboratory (Invitro, Helix and others).

The price of the service is in the range of 350 - 700 rubles, depending on the technique used.

For use at home, an immunochromatographic analysis of feces for occult blood has been developed. This is a quick and easy tablet test that reacts to human hemoglobin cells in faeces.

How to do the analysis yourself:

• Purchase a test for the diagnosis of hemoglobin in human feces at a pharmacy;
• Open the package;
• Collect feces with a special applicator in a container with a reagent;
• 2 drops of liquid drip on the indicator plate;
• Wait for the result.

Following the algorithm, it is possible to quickly and with a high degree of certainty (up to 99.9%) detect the presence of bleeding in the gastrointestinal tract: two strips - test and control, which means the fecal occult blood test is positive and you need to urgently contact a specialist.

Under the latent refers to blood that does not change the color of feces during macroscopic examination. Therefore, to determine the blood pigment, special reactions are used, based on the ability of blood to increase the rate of oxidative processes.

Why is an occult blood test performed?

This study will detect bleeding from the stomach, any part of the intestine and notice, for example, hemorrhagic anemia due to ulcerative lesions of the intestine.

In some conditions, the analysis of feces for occult blood is not performed: menstrual bleeding, the presence of blood in the urine, bleeding hemorrhoids, periodontal disease.

When is a fecal occult blood test ordered?

A stool test for occult blood is often done. The doctor sends for research in the following cases:

• pain in the abdomen of an unexplained cause;
• prolonged feeling of nausea in the absence of other signs of damage to the gastrointestinal tract;
• vomiting, recurring periodically;
• diarrhea for a long time;
• discovered helminth;
• Crohn's disease (inflammatory process in the gastrointestinal tract);
• ulcers in the stomach or intestines;
• the presence of bowel cancer in close relatives of the patient.

Study preparation

To accurately reflect the processes occurring in the digestive system, it is necessary to carefully prepare for the delivery of fecal analysis.

1. You need to start preparing about a week before the study. The attending physician should explain to the patient which medications can affect the result. And after the permission of the doctor, you can stop taking, for example, drugs that change the color of feces or laxatives.
2. At least 3 days before the analysis, it is necessary to review the menu. It is necessary to exclude meat, fish, offal (liver), as they contain a lot of iron and this can distort the result of the test.
3. When preparing for any study of feces, it is necessary to abandon products that color fecal masses (beets, carrots, tomatoes).
4. Bowel movements should occur independently: without laxatives, enemas.
5. 3 days before the analysis, it is necessary to refuse to perform diagnostic procedures (for example, an X-ray examination) or to carry them out later after the examination of feces.
6. You can not donate feces for research with menstrual bleeding.
7. It is forbidden to brush your teeth so that in case of bleeding from the gums and blood entering the gastrointestinal tract, there is no false positive result.
8. Before analysis, it is recommended to avoid penetration into the rectum, which can cause damage to the mucous membrane.

The collection of material for analysis is carried out at home in a sterile dry container, which can be bought at a pharmacy. As already mentioned, bowel movements should be independent without the help of any means. It is advisable to collect feces during the morning defecation after hygiene measures of the genitourinary organs and anus.

Feces should be delivered to the laboratory within 3 hours. If this is not possible, then storage of feces in the refrigerator for no more than 12 hours is allowed.

Examination of feces for occult blood

Normally, the reaction of feces to occult blood should be negative. There are several options for assessing fecal occult blood.

Gregersen reaction

The modification of the Adler test proposed by Gregersen is called differently benzidine test. A reagent is being prepared: benzidine, barium peroxide and acetic acid. Then it is dripped onto the prepared thin smear of feces. In the presence of blood, the color becomes blue-green. Table 1 lists the reasons for the positive Gregersen reaction.

Table 1 Causes of a positive benzidine test (Gregersen test).

The benzidine test is used to determine occult blood in other biological fluids (urine, gastric contents). 5-6 drops of the reagent are required per 1 ml of material.

According to the results of the benzidine test, it is impossible to say exactly from which part of the gastrointestinal tract the bleeding occurs.

Guaiac test

In 1864, Van Deen proposed a guaiac test for the detection of occult blood in the stool, later named after the author. The essence of the reaction is as follows: guaiac resin + hydrogen peroxide + heme = blue staining. A false positive reaction is possible if the diet is not followed.

With bleeding in the volume of 40 - 50 ml, the sample becomes positive. It is easy to perform and does not require expensive reagents; however, it is low sensitive for adenomas and cancer, and the frequency of false positive reactions is high, which has reduced the frequency of use in laboratory practice.

Immunochemical determination

A modern laboratory method for diagnosing occult bleeding from the intestines is an immunochemical test.

In the immunochemical determination, antibodies to hemoglobin and globin are used, so this test is more sensitive in detecting bleeding from the lower intestine.

The advantage of this method is that the reaction occurs only with human hemoglobin, the iron received from food or drugs does not affect the result. That allows not to limit the patient in eating habits.

For ease of analysis, immunochromatographic test strips (rapid diagnostics) have been developed.

The following are the conditions and diseases in which a positive occult blood test is noted:

Where is an occult blood test done?

The study of feces is carried out in any medical organization, both private and public. The cost of the analysis will depend on the determination method used by the laboratory: from 300 to 700 rubles.

Cancer of the rectum and colon is one of the most common causes of death from cancer. Early detection of colorectal cancer affects prognosis.

Fecal occult blood testing is considered as a screening method for the detection of colorectal cancer. In the case of a positive reaction, the patient is sent for a colonoscopy to detect a possible cause of blood in the gastrointestinal tract.

It is advisable to conduct a test for fecal occult blood in persons over 50 years of age every year. A triple analysis will allow you to confirm a negative result with high accuracy.

The final diagnosis is made in conjunction with clinical manifestations and additional research methods.

Fecal occult blood analysis captures even a small amount of blood, makes it possible to detect diseases at the primary stages, and this increases the likelihood of a favorable outcome. In the initial stages, the pathology is asymptomatic, and it is impossible to independently identify internal bleeding. The biological fluid in the feces can indicate a dangerous disease - from hemorrhoids to a malignant neoplasm.

• colorectal cancer;
• abnormal growth of tissues over the mucous membrane of the large intestine;
• ulcers, erosion of the stomach;
• diverticular disease of the colon;
• granulomatous enteritis;
• inflammatory processes that cause damage to the inner lining of the intestine;
• haemorrhoids;
• nonspecific ulcerative colitis.

In young children, this may be due to individual sensitivity to cow's milk. If the baby is breastfeeding, then the mother’s consumption of dairy products is to blame for bleeding.

Indications for the purpose of the analysis

The study is a typical method for detecting a malignant tumor of the colon and rectum at the initial stages of development.

The doctor prescribes the delivery of biomaterial in the presence of certain symptoms with which the patient addresses:

• abdominal pain, acid reflux, nausea, bouts of vomiting (follow this link to find out);
• systematically repeated false urge to defecate;
• regular constipation or diarrhea, fever, chills, lack of appetite, rapid weight loss;
• after detection of tumors in the gastrointestinal tract - diagnosis is necessary to exclude internal bleeding;
• helminths - a study is carried out to determine the degree of damage to the inner lining of the gastrointestinal tract (you will learn from this publication);
• previously discovered ulcers, Crohn's disease, infectious diseases caused by Mycobacterium tuberculosis.

Testing every 2 years is prescribed during preventive examinations after 50 years for the timely diagnosis of colorectal cancer. Indications for the test threaten health. If your doctor recommends a stool test, don't take it lightly. The process of passing a fecal occult blood test is absolutely safe and painless. The price of diagnostics varies from 300 to 750 rubles.

See in the next video what the indications for the appointment of a fecal occult blood test may be.

Types of analysis for occult blood

Laboratory research allows you to find biological fluid in the intestine. Research is carried out in two ways:
1

Benzidine test (Gregersen method)

The method detects the presence of hemoglobin even in a small volume, which is both an advantage and a disadvantage of this type of study. Used to record colorectal bleeding.
2

Immunochemical method

The fecal occult blood immunochemical test targets only human hemoglobin, so there is no need to follow a diet that excludes the use of foods rich in iron-containing protein before the test.

The method is not able to detect colorectal bleeding in the stomach, esophagus and duodenum.

Immunochemical appearance is more reliable, it will detect 0.05 mg of iron-containing protein per 1 g of the sample (with 0.2 biomaterial, the test is positive). The choice of the type of testing is made by the doctor and depends on the reason for issuing the referral for testing.

Preparation for analysis

The result of the test will be accurate if you follow the rules for preparing for delivery. They are different for each method (in this publication you will read how to prepare for the surrender).

Preparation for the analysis of feces for occult blood by the Gregersen reaction:

• Within 3 days before the delivery of the biomaterial, refuse to eat meat, liver and other products that contain iron (chickpeas, lentils, cashews, apples, dark chocolate, and so on).
• Within 3 days, do not take medicines, the component of which is iron, ascorbic acid, aspirin and non-hormonal anti-inflammatory drugs. Cancellation of drugs should be discussed with your doctor.
• Women are not allowed to donate feces for diagnostics during menstruation, 3 days before and after.

How to pass a fecal occult blood test, which is performed by an immunochemical method:

• It is not necessary to adhere to a special diet before analyzing feces for occult blood..
• If you regularly take medicines that increase the risk of bleeding, it is important to consult with your doctor about the procedure for conducting the study.
• It is forbidden to take the test for 14 days after passing the instrumental methods for diagnosing the digestive tract, which can lead to a violation of the anatomical integrity of the mucosa (these include colonoscopy, sigmoidoscopy, and others).

Compliance with the rules is the key to obtaining a reliable result of the study of the biomaterial.

How to properly collect feces

The sampling is carried out after spontaneous defecation (it is not allowed to take the biomaterial after using an enema or laxatives!).

The material is collected in a universal shipping container. You can buy a container in a pharmacy and laboratories.

The required sample volume is tsp. from 3 portions. It is forbidden to take areas with impurities of urine and secretions from the genitals. Material with blood is not examined.

Do not take material from the toilet. To do this, use a duck or a special vessel. In newborn babies, feces are taken from a cotton diaper immediately after a bowel movement.

How to take an analysis

Having received a referral for the test, the patient independently decides where to go for delivery: to a public medical institution or to a private laboratory.

Rules for storage and transportation of feces: up to 12 hours at a temperature of 4-8 ° C. The biomaterial must be delivered to the laboratory on the day of sampling.

How much is a fecal occult blood test done - it depends on the method chosen. The study by the immunochemical method takes about 14 days, and by the Gregersen reaction - 4 days.

There is a test for express research by an immunochromatographic method. For its implementation, a tablet has been developed that reacts to human hemoglobin cells in feces.

How to conduct an express study yourself:

• buy an express test for diagnostics at a pharmacy;
• open the package;
• to collect feces with an applicator in a vessel with a reagent;
• 2 drops of liquid add to the tablet with an indicator;
• wait for the result.

The appearance of two strips means that the diagnosis of the biomaterial for colorectal bleeding is positive, you should consult a doctor for further clarification of the circumstances. The correct use of the rapid test allows you to get a result with a reliability level of 99.9%.

Read in this how to decipher a urine test for protein levels.

How is the presence of blood in the stool determined?

The Gregersen reaction is carried out as follows: 0.025 g of basic benzidine and 0.1 g of a barium compound with oxygen are stirred, 5 ml of 50% ethanoic acid are added before the test. The reagent is shaken until a homogeneous solution is obtained.

A thin layer of the biomaterial is smeared onto a coverslip, then a few drops of the prepared reagent are added on top.

The color of the biomaterial in blue or green indicates the presence of biological fluid. This is due to the fact that when interacting with benzidine, the hemoglobin molecule is oxidized under the action of hydrogen peroxide and changes color.

Fecal occult blood analysis by the immunochemical method is based on the antigen-antibody bonding reaction between the human iron-containing protein present in the sample and anti-HbF antibodies on latex microspheres. The adhesion and precipitation of antigen-bearing cells from a homogeneous suspension under the action of specific substances is measured as an increase in absorption at 570 nm, the size of which is directly dependent on the level of hemoglobin in the sample.

Deciphering the results

Normally, in the human body there is an excretion of blood with feces in the amount of 2 mg or less of iron-containing protein per 1 g of material. A positive result indicates the presence of internal blood in the biomaterial. The intensity of the reaction is marked with a "+" sign: weakly positive ("+"), positive ("++" or "+++") and sharply positive ("++++").

In a healthy person, the result of a benzidine test is negative. A negative indicator is not significant for establishing a diagnosis.

Positive means that the stool contains more body fluid than normal.

This is a sign of the presence of diseases such as: stomach ulcer, inflammation of the duodenum, ulcerative colitis, malignant tumor of the stomach, thrombophlebitis, esophageal varicose veins, stomatitis, periodontal disease, periodontitis, bleeding from the gums or nasopharynx.

If the result is positive, it is necessary to re-test, since there is a possibility of an incorrect result associated with a deviation from the instructions for obtaining the biomaterial.

The norm of the result is the analysis of feces for occult blood by the immunochemical method: 0-50 ng / ml.

A positive fecal occult blood test indicates bleeding in the digestive tract. According to the test results, it is impossible to judge in which part of the digestive tract it occurs and what is the reason for this. To obtain additional data, endoscopic types of diagnostics (sigmoidoscopy, colonoscopy) are required.

When receiving a negative indicator, the presence of colorectal cancer cannot be completely excluded. Only a specialist should decipher the analysis of feces for occult blood.

Causes of False Positive and False Negative Results

In some cases, the result of a fecal occult blood test is false positive. The reason for this may be poor preparation for the collection of material. A false positive test may be due to bleeding from the gums and nose, causing the person to swallow a small amount of blood.

A false-positive result may be due to menstrual secretions entering the feces, as well as adherence to a meat and fish diet.

False-negative indicators can be if there is no free hemoglobin in the feces, but there are only undestroyed fresh red blood cells as a result of external bleeding (for example, from an anal fissure).

More informative 2-3-fold sampling of feces. This will eliminate false positives and false negatives. If the repeated test showed the initial result, then it is reliable.

conclusions

Based on what a fecal occult blood test shows, a diagnosis cannot be made. A positive result means that the disease is progressing, and in combination with the signs and symptoms that are manifested, allows you to designate a preliminary diagnosis.

Blood in the stool is a serious reason to see a doctor. It can appear for a variety of reasons. A ruptured hemorrhoid, anal fissure, allergies, helminths and protozoa in the intestines can cause bleeding. In a woman, blood may appear in the stool during menstruation. But blood can be a symptom of more formidable diseases.

There are colorectal bleedings, in which there is blood in the stool, but it does not leave a visible trace.

Such a diagnostic tool as a biochemical analysis of feces for occult blood can help to detect it.

Indications

Blood in the stool can be present in people of all ages - in a newborn baby, infant, adult men and women. The reasons for an adult and a child for which there is blood in the stool may coincide, but may also be due to age criteria.

In what cases is it necessary to donate feces in order to do an occult blood test? Indications for examination are:

• pain sensation in the abdomen of a constant or periodic nature;
• regular feeling of nausea or vomiting;
• heartburn;
• chronic diarrhea or constipation;
• weight loss without dietary restrictions;
• the need to confirm a particular disease (ulcers, gastritis, etc.).

What do you need to know about analysis?

Today, you can conduct a similar analysis yourself at home. You can buy express tests in pharmacies. How can they correctly determine the presence of blood?

1. It is not easy for a person who does not have special skills to comply with all the conditions, to accurately reproduce the procedure (many manipulations) when performing the test.
2. The test result largely depends on the quality of the sample.

It is easier and more reliable to conduct a study of feces in a specialized laboratory.

In the laboratory, three methods are used to determine blood inclusions in feces:

• Gregersen reaction (benzidine test):
• guaiac test (Weber test);
• immunochemical method.

1. In the first method, feces are applied in a thin layer on a glass slide and a reagent is dripped onto it. The composition of the reagent includes benzidine, barium or hydrogen peroxide, acetic acid. The blood content shows a bright blue or green color of the test sample.

The method is simple, allows you to detect blood at a very low concentration. But he has a significant drawback - a positive reaction can be given by eaten meat food or blood that has entered the intestines from bleeding gums.

To obtain more reliable information, thorough preparation is needed. Three days before the test, all foods containing iron are excluded from the menu, you can not drink non-steroidal anti-inflammatory drugs, laxatives.

1. Similarly, you need to prepare for the delivery of feces for a guaiac test. At the slightest violation of preparation, a false positive result is possible. The quantitative side is also important - blood loss should be at least 50 milliliters.

The essence of the method is that a small amount of feces is ground with acetic acid to the state of liquid porridge, then hydrogen peroxide is added and titrated with tincture of guaiac resin. A chemical reaction is considered positive if a blue or violet color occurs.

1. The most accurate is the immunochemical method. The method is called so because it reacts exclusively to human hemoglobin. Animal hemoglobin from food and iron from drugs do not affect the result. This is a definite plus, since it will not cause trouble for the patient due to severe dietary restrictions and exempts from the ban on taking medications.

What does immunochemistry show in this context? It can detect the following diseases:

• polyps;
• colorectal cancer;
• Crohn's disease;
• ulcerative colitis.

Diet

1. It is not difficult to prepare for an immunochemical analysis. There is no need to follow a diet - you can eat everything.
2. With the other two methods, a diet with the exclusion of foods high in iron is required.

How to collect and donate feces?

Feces should be collected only after spontaneous bowel movements. With all methods, enemas should not be done so as not to accidentally damage the intestinal mucosa.

For a sample to be valid, it must not be contaminated with urine. For the same purpose, the baby takes feces not from a diaper, but from an oilcloth.

Decryption

The received data is entered into a table. Their decryption is carried out by a specialist. The normal result of the analysis is one - negative. A positive result is not very good.

The program of further actions is determined by the doctor. As a rule, it includes an examination of the intestine using colonoscopy, the delivery of urine and blood for general and biochemical tests to determine the level of tumor markers. After an additional examination, appropriate therapy is prescribed.

Blood in the feces is a pathological sign, but you should not make gloomy predictions. It is necessary to take a responsible approach to treatment and lead a healthy lifestyle. With early detection of pathology, it is possible to cure cancer.

For more information on the topic "How to donate feces for occult blood" can be obtained by watching the video:

During normal operation of the gastrointestinal tract, a small amount (about one milliliter) of blood is excreted in the feces, which is not detected by laboratory methods.

However, doctors often encounter bleeding from the gastrointestinal tract. Often, such bleeding is caused by the presence of neoplasms in the organs of the gastrointestinal tract. In particular, with a tumor of the colon, the process of bleeding can begin already in the asymptomatic, early stages of the disease, then blood enters the intestinal lumen. An occult blood test is prescribed for stomach or duodenal ulcers, polyps, erosions, intestinal neoplasms, hemorrhoids and other conditions when bleeding from the gastrointestinal tract may be suspected. In addition, this analysis is necessary for screening in people over forty-five years old. This review is done at least twice a year.

Currently, a large number of screening methods have been developed to detect asymptomatic diseases of the gastrointestinal tract even in supposedly healthy people at an early stage, which makes it possible to achieve a positive result in the treatment. Blood that is not determined macro- and microscopically, and does not affect the color of feces, is called latent. There are methods for detecting this hidden one as well. For this, special reactions are used, which are based on the property of hemoglobin to accelerate oxidative processes. These are the so-called guaiac or benzidine samples.

In order to prevent false results, the patient should be prepared in a special way before the study for occult blood. Firstly, already in three days, foods containing a large amount of catalase and peroxidase should be excluded from the diet, these include horseradish, cauliflower, cucumbers, you can also not use acetylsalicylic and ascorbic acids, non-steroidal anti-inflammatory drugs and iron-containing drugs. Feces can be examined after three consecutive bowel movements, and each time a sample for analysis is taken from two different areas of the stool. If at least one positive result is obtained, it is considered diagnostically significant. This is true even when the postulates of proper patient preparation have not been observed.

And there are such requirements. In particular, a day or two before fecal sampling for analysis, laxative drugs should not be used, enemas should not be done.

Feces should be collected in a special plastic container. Before collecting feces, the patient must urinate into the toilet. Next, a natural defecation should occur in the toilet, or a bedpan, after which the feces are collected. Collect feces into the container with a spoon, and the container should be filled to a third of the volume, no more. It is impossible to collect feces together with urine. A label must be attached to the container, which indicates the full name. patient and date of sampling.

The results of the analysis can be significantly affected by the use of laxatives, castor and mineral oils, radiopaque substances less than three days before the study, the sampling technique, in which urine enters the feces.

The benzidine reaction determines blood loss, which in volume exceeds fifteen milliliters per day, it is also characterized by an increased number of false positive results, so it is currently used little. The most common now guaiac test, where the frequency of positive results is associated with the amount of blood in the stool.

A more reliable occult blood test has now been developed and is used for early detection of colonic neoplasms. This is an immunochromatographic test, specific antibodies to human Hb are used here. These tests favorably differ from the outdated benzidine test and from the not so accurate test with guaiac resin, in that the reaction only to human hemoglobin is checked here. In addition, there are no restrictions on nutrition and the use of drugs. These tests are highly sensitive, even six thousandths of a milligram of Hb per gram of feces are found here, although even values ​​\u200b\u200bof more than 0.2 mg / g are already a positive result. Immunochromatographic tests are also used for the targeted diagnosis of neoplasms of the large intestine, since they are not able to detect bleeding from the upper gastrointestinal tract.

A positive fecal reaction to occult blood can mean gastric and duodenal ulcers, intestinal tuberculosis, primary and metastatic tumors of the gastrointestinal tract, the presence of helminths that injure the intestinal wall, ulcerative colitis, anal fissures and, bleeding from varicose veins of the esophagus and simply blood during menstruation in feces in women.