How long does a fecal occult blood test take? How to properly donate feces for occult blood with various methods of examining feces

In medicine, this method of studying human feces is carried out as a diagnosis of diseases of the intestines or stomach. A fecal occult blood test can be prescribed for both children and adults. It also helps to identify what is contained in red blood cells, even if the red cells themselves are not found in the analysis.

What it is

Patients often ask the question: fecal occult blood test, what is it? The study has a different name - the Gregersen method and is carried out on feces, which are collected by the patient in a sterile container in conditions of complete purity of the material.

Training

Preparation for the analysis of feces for occult blood includes several stages:

• Four days before your scheduled fecal examination, you must not eat the following foods: tomatoes, meat, fish and all green vegetables.
• Any type of laxative to speed up the process of excretion of feces is prohibited. Do not use rectal suppositories.
• If you use certain medicines every day, you should tell your doctor about it, because taking some of them affects the color of feces and they should be excluded from use for four days.
• This occult blood test is mandatory before any tests in the stomach and intestines, and not after them.

The analysis of feces for occult blood is very important in medicine, because it allows you to tell about problems in the stomach and intestines long before they manifest themselves in any other way. Preparation for the analysis of feces for occult blood and the study of feces in humans allows you to talk about the hidden and prevent its consequences. It can also reveal the presence of an oncological tumor in a patient, which he does not even suspect. In this case, you need to start treatment as soon as possible.

Blood may not be visible in the stool on visual examination. But, even if a blood test for occult blood is normal, and no deviations are noticed, then it still needs to be taken just for prevention.

If we talk about feces for occult blood, then it can also be carried out visually if there are certain symptoms. If it is observed, or rather, in its lower sections, then the blood will be bright scarlet in color or it will contain impurities. If there is a suspicion of, then the stool will be black and appear thicker than with a normal bowel movement.

If you observe changes in fecal masses, and they are visible even to the naked eye, then you need to urgently contact a specialist. This may be any serious disease that requires immediate treatment. If you notice even an insignificant change during defecation, then you still need to start an examination, because it will help to prevent the development of the disease in time.

Purpose

An analysis for occult blood in the feces is prescribed to patients with suspected various diseases, and in particular, with the following patient complaints:

• Abdominal pain, heartburn, nausea and vomiting (such anomalies indicate problems with the intestines or stomach).
• If the patient has an upset stomach or constipation (moreover, these are frequent phenomena), the patient loses his appetite, weight decreases, and his body temperature is constantly elevated.
• If a malignant tumor is found in the patient's stomach or intestines, which is treated with instruments.
• A stomach ulcer, discovered long ago and not cured.

Decryption

If, as a result of the study, blood is still detected in the feces, then deciphering the analysis of feces for occult blood may indicate the following pathologies:

• The patient may have an ulcer of the duodenum or stomach.
• Tuberculosis of the intestine.
• Colorectal cancer (meaning there is a malignant tumor).
• Tumors of the stomach or intestines or metastases.
• Rendu-Osler disease.
• Nonspecific ulcerative colitis.
• If you have thrombophlebitis or cirrhosis of the liver, then the result of the analysis is confirmed.
• Bloody stool is the first sign of hemorrhoids.
• Erosive esophagitis.
• Periodontal disease or stomatitis of the oral cavity.
• If the patient is disturbed every day.

Many patients do not pay attention to the symptoms of these diseases and therefore often start treatment. It should be remembered that if one of them was revealed during the analysis of feces for occult blood, then it is simply necessary to start treating it right away. To do this, follow the advice of your treating specialist.

A blood test may indicate the presence of chronic anemia if the patient has intermittent bleeding.

In the event that there is no obvious bleeding, doctors continue the diagnosis, until the discovery causes of anemia.

A routine blood test cannot determine the source of the bleeding. Therefore, to determine the cause, additional tests are carried out, including a fecal occult blood test, which allows you to find blood in the gastrointestinal tract.

A fecal occult blood test is a study designed to to diagnose minor bleeding from any part of the digestive tract. The analysis owes its name to the fact that it is quite difficult to detect a small amount of blood in the feces. A small amount of blood does not change either the consistency of the feces or its color. This means that bleeding can be detected only with the help of special tests.

An occult blood test helps to detect erythrocyte hemoglobin when this cannot be done either by microscopic examination or visually.

During a laboratory test, hemoglobin is looked for in a stool sample. To do this, a reagent is added to the feces, which, interacting with hemoglobin, contributes to the appearance of a chemical reaction. This technique makes it possible to identify the presence in the gastrointestinal tract of even a slight bleeding.

In other words, analysis can reveal even hemoglobin, which the day before got into the stomach of a person during a meal. In order to avoid such a mistake, it is necessary to properly prepare for the delivery of the analysis.

A positive analysis indicates the presence of an ulcer, oncology or inflammation, so even a tiny amount of blood in the digestive organs is a cause for concern. It must be remembered that in some cases, the analysis may not correctly reflect the picture of what is happening.

The reason for the false result may lie in improper preparation to the delivery of the analysis and in other bleeding - from the nose and from the gums. In order to make sure that the result obtained is correct, the stool analysis must be taken twice, with an interval of several days. In the event that the test gives the same “verdict” twice, it can definitely be trusted.

Training

Any doctor who has doubts about the health of the patient can prescribe an occult blood test: a general practitioner, gastroenterologist, oncologist or surgeon. In this case, the doctor must warn the patient that it is necessary to properly prepare for the test. This preparation includes the implementation of certain recommendations.

• 7-10 before analysis stop taking the following drugs: laxatives, anti-inflammatory, bismuth- and iron-containing, non-steroidal. Also during this time it is forbidden to take acetylsalicylic acid and drugs in which it is present (Aspirin).
• Stop the introduction of rectal suppositories, oils.
• Don't give enemas.
• Within 1-2 days before the delivery of stool samples, do not conduct any diagnostic studies in the gastrointestinal tract. If this requirement is not observed, it is possible to injure the mucous membrane and, as a result, obtain an unreliable result.
• Observe special diet within 72 hours before donating feces.
• Give up the habit of brushing your teeth for a while. The smallest amount of blood that appears when the gums are damaged is highly likely to enter the gastrointestinal tract.

What can you eat?

To get a reliable result, 72 hours before the study, you must "go on a diet". This diet does not prohibit eating dairy products, potatoes, some cereals and bread. The main thing is to avoid eating foods high in iron.

If you are in doubt about what foods you can and cannot eat before taking the test, talk to your doctor about this topic.

Prohibited Products

Three days before taking a stool sample for occult blood eliminate the following foods from your diet:

• some fruit and vegetable crops, namely: apples, white beans, cucumbers, spinach, cauliflower, horseradish);
• meat and chicken dishes, offal, fish dishes;
• green vegetables, tomatoes;
• iron products e.g. bell pepper.

Failure to comply with this requirement is fraught with the fact that the smallest particles of hemoglobin will get into the feces, the results will be unreliable, and the test will have to be done again. To avoid such a development of events, carefully prepare for the analysis and do not neglect the recommendations of your doctor.

Usually, the appointment of a fecal occult blood test has a good reason. If the doctor has written you a referral for this analysis, you must pass it as soon as possible. If you get a positive result, you should not panic.

Remember: the sooner the disease is detected, the sooner treatment will be prescribed that can eliminate this pathology and restore your lost health.

Bleeding is considered a dangerous symptom in diseases of the gastrointestinal tract, which means that it requires immediate medical attention. The pronounced red color of feces leaves no doubt about the presence of pathology, but the latent course progresses for a long time and imperceptibly, which leads to severe complications. Visually, abnormal inclusions are not detected, therefore, it becomes possible to make a correct diagnosis only after laboratory tests.

The essence of the analysis

A fecal occult blood test shows the presence of blood particles that cannot be seen under a microscope during a coprogram. Such a study is one of the most common and allows timely detection of bleeding from the organs of the gastrointestinal tract.

Violations of the integrity of the mucosa can occur in the upper or lower digestive system. In the first case, blood particles undergo biochemical processes and, getting into the feces, acquire a burgundy or brown color. If tissue damage has occurred in the large intestine, the detected discharge remains scarlet.

In severe diseases, such as malignant, occult blood is the only symptom of the initial stage. Timely diagnosis makes it possible to start the right treatment and preserve the health of the patient.

When an examination is ordered

The analysis is carried out when a life-threatening disease is suspected, or to identify the cause of pathological conditions associated with metabolic disorders. Indications for the study of feces for blood are as follows:

• Helminthiasis.
• Persistent vomiting, heartburn, or nausea.
• Gastric ulcer.
• Abdominal pain of unknown origin.
• Liquid stool.
• Excessive weight loss.
• Diagnosis of the state of the mucous organs of the gastrointestinal tract.
• Digestive disorders.

In addition to all these situations, doctors prescribe a stool study at their discretion. It is better for the patient to agree with the doctor and conduct an additional analysis, as it will help to make the most accurate diagnosis. Thus, the reaction to occult blood is necessary to obtain information about the presence of damage to the walls of the digestive organs.

Types of occult blood tests

Modern research methods are more accurate and revealing than those used a few years ago. There are two methods to help detect occult blood.

Benzidine test

It was popular for a long time, as it made it possible to determine even low concentrations of blood components. The principle of action is based on the detection of hemoglobin, the main component of red blood cells. To do this, a chemical reaction is used, as a result of which the iron in the heme is oxidized by hydrogen peroxide and becomes blue.

The disadvantage of the method is its non-specificity. That is, a positive reaction is obtained when exposed to an iron atom of any origin, even animal and vegetable. Because of this, the patient needs to undergo special training, where it is important to follow a certain diet.

Immunochemical analysis

It is a more accurate study. It is prescribed both independently and in addition to other methods to clarify their results. The principle of operation is different from the previous one. Here, the basis is the determination of the concentration of specific antibodies that are produced in humans in response to antigens. The method is more often used in pathologies of infectious genesis. Among the shortcomings, the duration of execution is noted - the final results and the diagnosis become known only after 1-2 weeks.

No type of analysis involves internal interference or additional damage. The high sensitivity of the reagents requires some preparation of the patient in order for the results to be reliable.

Preparation for analysis

• Drugs that can affect the results are canceled 1 week before the analysis.
• The day before the study, it is necessary to exclude possible damage to the oral cavity, including when brushing with a hard toothbrush or eating solid food.
• Women should be tested during the absence of menstruation.
• A few days before taking the biomaterial, you need to follow a diet. You can not eat foods containing iron (meat, fish, tomato, beets). With the immunochemical method, restrictions may not be observed.
• Previously, it is not allowed to carry out artificial emptying with enemas and laxatives (even based on herbal ingredients).

How to properly collect feces?

The rules for taking biomaterial are as important as preparing for analysis. The test sample must be fresh, so the stool is delivered to the laboratory as quickly as possible.

To properly pass the analysis, you need to be guided by the following recommendations:

• Prepare a container for collecting biomaterial. It is better to use special jars that are sold in pharmacies and already contain spatulas for sampling.
• After defecation, collect dry stool residue without water and urine, which may accidentally fall on them. It is better to do this in the morning so that the biomaterial is immediately taken to the laboratory.
• The amount required for the study is 3 fragments of feces, which are taken from different sites. To do this, use a teaspoon or spatula from a pharmacy container.
• The biomaterial must be delivered to the laboratory not later than 3 hours. Until then and during transport, it is recommended to keep the material sample in a refrigerator.

Deciphering analyzes

The results of the analyzes are compared with indicators that are considered normal. Doctors allow up to 2 ml of blood to enter the intestines daily. If the detected particles are greater than this number, the result is considered positive and the doctor has reason to suspect internal bleeding. When occult blood is not detected or its concentration is less than 1 mg per 1 g of feces, the results of the study are considered negative. Doctors take into account only elevated values.

Due to improper preparation for the study, the result is always erroneous. Doctors note that data distortions occur both in the direction of positive results and negative ones. In order not to doubt the obtained indicators, it is recommended to repeat the study even without any reason.

It is known that in some diseases, pathological bleeding is observed not constantly, but periodically, and this makes it difficult to detect. If the preliminary diagnosis is known, for example, intestinal polyps, then the absence of hemoglobin will raise doubts and a second analysis will be required. That is why doctors prescribe several types of examinations for diagnosing a patient - laboratory, instrumental.

What does a positive result mean?

An increased amount of hemoglobin in the feces often confirms damage to the digestive tract and the presence of pathologies. A positive analysis suggests one of the following conditions:

• Crohn's disease.
• Bleeding caused by varicose veins of the esophagus.
• Malignancy or polyps.
• Nonspecific ulcerative colitis.
• Fissure of the anus, mechanical damage due to constipation or hemorrhoids.
• Oral problems.
• Helminth infestation.
• Ulcerative lesions of the stomach or duodenum.

Since a positive result suggests serious pathology, the patient should verify the reliability of the data obtained and repeat the analysis. Small errors in nutrition or accidental damage to the oral cavity lead to false readings, and therefore it is important to properly prepare for the first examination.

The method of re-examination is chosen by the doctor - this may be a second laboratory analysis or examination of the intestine using an endoscope. Often, when confirmation of the presence of occult blood is obtained, especially by immunochemical method, the patient is also recommended to do a colonoscopy.

An additional examination of the intestine will help confirm or refute the presence of bleeding polyps or other neoplasms. The feasibility of the double examination algorithm has been proven in screening programs. Thanks to this approach, the mortality of patients was reduced by 25%.

Pathologies of the duodenum, stomach, esophagus may be accompanied by internal bleeding. Stool analysis helps to identify them at an early stage. The study reveals occult blood, which often becomes a sign of cancer.

What is occult blood in stool

Traces of blood that are invisible to the human eye in excrement are called occult blood. They are found only during special tests for the detection of transferrin or hemoglobin. The study gives the most reliable results in identifying such pathological conditions:

• duodenal ulcer, stomach;
• helminths in a child;
• tuberculous lesions of the intestine;
• blood diseases;
• varicose veins of the esophagus;
• Crohn's disease;
• erosive esophagitis;
• cirrhosis of the liver;
• Lynch syndrome;
• hemorrhagic diathesis;
• tumors;
• polyposis;
• inflammation of the palatine tonsils, pharynx.

Analysis of feces allows you to detect colorectal cancer, intestinal tumors at an early stage. Positive test results are typical for such pathologies:

• diverticula of the intestine, stomach;
• erosive gastroduodenitis;
• nonspecific ulcerative colitis;
• damage to the mucous membrane of the digestive system.

When is an occult blood test ordered?

Doctors prescribe a fecal examination to the patient when signs of diseases of the digestive system appear. Indications for the study are the following symptoms:

• abdominal pain of unknown etiology;
• false urge to defecate;
• causeless loss of body weight;
• diarrhea;
• constipation;
• hyperthermia;
• nausea;
• heartburn;
• vomit.

Methods for detecting occult blood in feces

When internal bleeding is suspected, doctors use different methods for examining feces. They differ in sensitivity, efficiency, the need for preparation, the definition of pathologies in various parts of the intestine. Diagnostic methods for occult blood, their advantages and disadvantages:

Benzidine test

This analysis of feces for the detection of hidden blood loss has a second name - the Gregersen test. The main reagent is benzidine, to which acetic acid and barium peroxide are added to increase activity. The technique gives a lot of false positive results - a reaction to nosebleeds, eating meat, drugs, bleeding gums.

Immunochemical test

Operative research reveals neoplasms in the colon at an early stage, reduces cancer mortality by 30%. Immunochemical analysis of feces for occult blood reacts only to human protein, does not require special preparation. It is characterized by high sensitivity and such features:

Guaiac test

The sensitivity of the guaiac test depends on the concentration of hemoglobin. If its content is more than 2 mg per gram of feces, the result is positive in 90% of cases. The test diagnoses bleeding in any part of the digestive system. The analysis has the following specifics:

Rules for preparing for the study

To obtain an accurate test result, proper preparation is essential. The process begins a week before the analysis, includes the following activities:

Features of preparing for the Gregersen test

To eliminate the error in the results of this technique, it is important to strictly follow the diet. The Gregersen test for occult blood is sensitive to iron, pigments from food. It is necessary to postpone research for a while under the following circumstances:

• the presence of blood in the urine (hematuria);
• menstruation in women;
• hemorrhoids with bleeding;
• periodontal disease;
• indigestion (dyspepsia);
• breaks, damage as a result of anal sex.

An important role is given to the correct sampling of material for analysis. The following conditions must be met:

• conduct hygiene of the genitals, anus;
• collect feces in the morning, before breakfast;
• ingress of water, urine is unacceptable;
• you can not take biomaterial from the toilet (you need to put an oilcloth);
• fragments must be from three places;
• put the feces in a special sterile container;
• deliver to the laboratory within two hours.

Deciphering the analysis of feces for occult blood

The physician interprets the test results. The immunochemical test is considered the most accurate, but it is not performed in all laboratories. It takes 1-3 days to conduct and decipher the analyzes. Experts recommend, upon receipt of positive and negative results, to conduct an additional re-examination of feces for the presence of hidden bleeding and diagnostics using instrumental methods.

Negative result

If a small amount of blood enters the intestines, in a healthy person, under the action of enzymes, it decomposes. The norm is 0.2 mg of hemoglobin per gram of feces. A negative result confirms the absence of bleeding in the body, dangerous diagnoses, or requires a second examination when the patient has signs of pathologies.

Positive

If a patient is suspected of having occult bleeding, a positive test result is possible. Often it indicates an early stage of diseases associated with damage to the mucous membranes:

• colorectal cancer;
• peptic ulcer;
• intestinal tuberculosis;
• tumors of the digestive system;
• helminthiasis;
• pathologies of the veins of the esophagus;
• hemorrhoids.

Positive test for occult blood in a child

When analyzing feces in children, signs of hidden bleeding are sometimes revealed. The reason for a positive reaction depends on age:

False positive and false negative results

Often, studies of feces for the presence of hidden blood loss give ambiguous results - false negative, false positive. In this case, it is necessary to perform repeated analyzes, conduct additional diagnostics. A false positive response is possible in such cases.

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:

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:

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 300-400 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.