How to collect feces for occult blood. Analysis of feces for occult blood. Is it so important how to collect materials for research

Taking feces for analysis to detect the presence of occult blood is one of the modern diagnostic methods that allows you to timely identify a number of serious diseases of the gastrointestinal tract. Probably every adult knows that blood in the stool is dangerous. And when spotting is found in their own feces, many consciously rush to go to the doctor. But the fact is that the stage when blood is clearly visible in the feces is far from the first stage of the disease. And often the success of treatment when this kind of bleeding is detected is not as clear as if the blood had been detected earlier.

Many diseases of the digestive system, the entire complex digestive system, at the initial stage may not manifest any symptoms, and even more so - profuse internal bleeding. But blood microparticles are already present in the body and are excreted from it along with feces. Only they are so small that it is impossible to see them, even by peering intently at their own excrement (which most people usually do not, for obvious reasons). This is where an occult blood test is performed.

Today, this analysis is prescribed to all patients who have reached the age of fifty, one-time, annually. Age groups under 50 take it according to indications.

In what cases is this analysis prescribed? Why do doctors suddenly start looking for hidden blood in a patient's stool? This is done when a number of diseases are suspected.

Fecal occult blood sampling is a common laboratory test, such as a complete blood or urine test. With it, you can identify implicit internal bleeding, which is present:

• in any part of the intestine;
• in the stomach;
• in all organs of the digestive system without exception.

Agree, it is quite difficult to “see” what is happening inside the digestive system, especially in the endless intestine, the total length of which is about eight meters in an adult (five times his height). Moreover, the structure of the intestines is intricate, and the arrangement is tortuous.

By the way. At the same time, the digestive and excretory tract is the most “risky” organ, containing a record number of bacteria, through which toxic and other waste products of the entire body are excreted. Here it is easiest to "hide" harmful microbes, tumors, tears and damage.

Indications

Doctors prescribe a fecal occult blood test quite often. Indications for analysis may be the following symptoms and complaints of the patient.

1. Abdominal pain (localized in the abdomen) of unclear etiology.
2. A feeling of nausea that continues for a long time in the absence of diagnosed gastrointestinal diseases.

   

3. Recurrent vomiting.
4. Persistent loose or loose stools.



5. Diverticulitis.
6. Identified helminthiasis.



7. Loss of body weight for no apparent reason.
8. Cirrhosis of the liver.
9. Diagnosed pathologies of the gastrointestinal tract.



10. Ulcerative lesions of the stomach.
11. Ulcers in the intestines.



12. Colon or colorectal cancer in a close relative of the patient.
13. Damage to the mucous membrane of the digestive organs.

There are conditions under which a fecal examination that detects occult blood cannot be performed until a change in circumstances:

• dyspepsia;
• menstruation;
• bleeding hemorrhoids;
• hematuria (when blood is found in the urine);
• periodontitis.

In parallel with the study of feces, a leukocyte blood test, biochemistry, a general urine test, kidney tests and tumor markers are prescribed.

Important! If you receive a positive test result that was detected in the laboratory or during the test at home, a colonoscopy of the intestine is recommended. The obtained negative result reduces the risk of the presence of most formidable diseases, but does not completely exclude it. It is necessary to compare the result with other tests prescribed in parallel.

How to increase research efficiency

The effectiveness of the study depends on how carefully the patient prepares for the test. The scrupulous fulfillment of all the requirements for the patient is the key to the accuracy of the result.

General preparation for the delivery of feces for occult blood is carried out as follows.

1. Start of preparation - 7 days before the analysis. Since that time, all medicines that tend to stain the feces in any color are canceled. It is also necessary to stop taking medications that affect intestinal motility.

   

   As prescribed by the attending physician, one week before the fecal donation procedure, all medications are canceled

2. Three days before the delivery of feces, the following is excluded from the menu: meat, fish, offal, tomatoes, beets, peppers, broccoli, beans, spinach, apples, green onions. This is necessary to prevent distortion of the color picture.

   

3. Also, for three days, the use of vegetables and fruits, which can affect peristalsis, is stopped.

   

   Vegetables, fruits, juices that affect peristalsis are excluded from the diet

4. You can not take laxatives and cleanse the intestines in any other way than the natural way, especially with the use of an enema.

   

5. Later than three days before the test, X-ray examinations are not carried out, since they may use reagents that can distort the results of the analysis.

   

   Radiography is done no later than three days before the study of feces for occult blood

6. Before taking feces for analysis, women must completely end their periods (during menstrual bleeding, analysis is not performed).

   

7. On the eve of the delivery of feces, you should not brush your teeth, so that in case of accidental damage to the gums with a brush, blood fragments do not get into the feces.

   

8. Also, you can not have anal sex to prevent the formation of mechanical damage and ruptures with resulting bleeding.

   

   Before the test procedure, it is important to avoid any traumatic penetrations.

Important! Blood hidden in the feces is an indicator of multiple diseases, but most importantly, it can be a signal of malignant diseases. The very first warning about the appearance of cancerous tumors in the intestines throughout its area, the esophagus and stomach. Of course, the earlier cancer treatment is started, the more likely it is to win.

Analysis sampling rules

When collecting feces for analysis, a number of rules must be observed.

Important! The study is carried out over six days. The result of the norm is negative. This does not mean that there is absolutely no blood in the feces. But this means that its presence does not exceed acceptable limits. If the norm is exceeded, the result is declared positive.

Types of analysis for occult blood in the feces

This test can be done in three different ways. The test material is analyzed using:

• guaiac test;
• immunological test;
• Gregersen reactions.

Table. Type of analysis and description.

The specifics of preparing for the guaiac test

Before passing the guaiac test for three days, it is necessary to remove from use:

Specifics of preparation for the benzidine test

Here, too, it is important not to violate the rules of preparation and carefully observe them.

From the menu are excluded three days before delivery:

Deciphering the results

The test can be positive or negative. In the second case, this means that the blood expires normally. In any case, blood is secreted in the body of every person. It moves through the intestines, breaking down under the action of enzymes, but if its amount does not exceed 0.2 mg of hemoglobin per 1 g of feces, the result is considered negative, and blood in the feces is recognized as absent.

With a positive result, the values ​​\u200b\u200bexceed the declared indicator, sometimes by several tens of times.

It should be borne in mind when deciphering that the sample can be either false negative or false positive. If there is bleeding of a non-permanent nature, for example, with polyps, a negative result may be found in this analysis. For an accurate diagnosis, it is necessary to repeat the test.

Conversely, in case of accidental trauma to the mucosa, even if it happened during the morning brushing of teeth or nosebleeds that happened the day before, as well as when using foods and preparations containing iron, the result can be positive in the absence of any disease.

Important! If the test is negative, then it must be repeated and confirmed. If the sample is positive, it is also recommended to conduct a confirmatory analysis and prescribe further examinations to the patient.

The importance of this analysis in the diagnosis of most gastrointestinal diseases is very high.

There are bleeding open and obvious, changing the stool to such an extent that you can visually determine their presence. For example, when blood flows out of the lower segments of the colon, it stains the feces scarlet, and can be collected in large clots or wide veins. With a source of bleeding, which is located in the upper part of the gastrointestinal tract, the feces darken, acquire the color and texture of tar, since the blood, reacting with gastric enzymes, modifies it.

Important! With visually detected bleeding, the situation is certainly an emergency, requiring immediate medical attention, up to and including surgery. But this does not mean that hidden bleeding is less dangerous.

Traditional tests have many shortcomings and errors, however, the study of feces for the presence of occult blood helps to diagnose many diseases so effectively that there is no such safe and painless, non-traumatic and quick alternative.

Tests for the presence of blood are positive in 97% of episodes of colon cancer, in 60% of adenomatous polyposis (1 cm in diameter) and other dangerous diseases. Statistically proven that the detection of cancer in the initial stages reduces the mortality rate from this disease by an average of 30%.

Video - Analysis of feces for occult blood

Fecal occult blood testing is widely used to diagnose bleeding in the gastrointestinal tract. With improper preparation or incorrect collection of material, false positive reactions may occur that change the diagnostic picture. Therefore, you need to know how to properly prepare for the study.

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.


To date, there is an analysis that does not require special preparation of the patient. This is an immunochemical fecal occult blood test. It is based on the interaction of antibodies only with human hemoglobin, so the analysis is more specific and sensitive than standard chemical tests.

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.

Blood in the feces indicates various pathologies of the gastrointestinal tract. Sometimes it is visible to the naked eye, and some diseases are characterized by hidden hemorrhages. Therefore, for certain indications, a fecal occult blood test is prescribed. This test allows early detection of serious diseases. In 50%, a positive reaction indicates a tumor lesion of the intestine. It is necessary to take the analysis after special training, otherwise, regardless of the chosen method of determination, the result will be unreliable.

Indications for fecal occult blood testing

Hidden hemorrhages from the gastrointestinal tract do not cause significant changes in the composition of the blood, do not lead to anemia. Fecal occult blood analysis is necessary for the early diagnosis of such pathologies:

• , duodenal papilla;
• that injure the intestinal mucosa;
• , thrombophlebitis of the spleen, accompanied by;
• Rendu-Osler disease;
• and etc.

Without fail, a screening study for the detection of hidden hemorrhages is prescribed in risk groups for oncological diseases of the intestine. It is recommended that the Hemacult test (rapid analysis for detecting occult blood in the feces) be done annually to patients:

• over 50 years old (absolutely everyone);
• older than 45 years (if there is a family history of bowel cancer).

To pass the analysis, you need to prepare, otherwise, instead of valuable diagnostic information, you will get a false positive or false negative result.

Study preparation

Hidden blood in the feces is found not only in diseases of the gastrointestinal tract. This may be the result of nose or gum bleeding (due to intensive brushing of the teeth). In addition, the reagents used to detect hemorrhages react to hematin, and hematin can enter the stomach and intestines with food.

In order not to get a false positive test result, you must:

1. 3 days before the study, refuse to eat meat products, fish. Green plants should also be excluded from the diet, they, like blood, catalyze the oxidation reaction of benzidine, guaiac resin and give a positive reaction.
2. 3 days before the analysis, the possibility of even minor hemorrhages from the oral cavity and nose should be excluded. Teeth should be brushed with extreme care. Avoid very hard foods (crackers), as you can damage the oral mucosa. Even minor bleeding will give a positive result. If it was, then it is better to reschedule the study.
3. Women are not recommended to take an analysis 3 days before menstruation, during them and within 3 days after them.
4. An analysis for the detection of occult blood in the feces precedes x-ray, endoscopic studies. After using these diagnostic methods, there is a high probability of getting a false positive result.

Sometimes occult blood is not found in the stool, even if it is there. The reason for this is the wrong material intake. In order not to get a false negative analysis, it is necessary to collect material from different places of the feces.

A screening study for the presence of hidden hemorrhages is carried out 3 times (if the first time the result was negative). This is necessary, since bleeding does not always occur with tumors. In the early stages, they may be absent or appear and then disappear.

The result of the analysis depends on the chosen method of determination.

How is occult blood found in stool?

There are several methods for detecting blood in the stool. Most of them lie in the ability of hemoglobin to break down hydrogen peroxide, while changing the color of easily oxidized substances:

• benzidine;
• guaiac resin;
• phenolphthalein;
• pyramidon.

In clinical practice, they resort to such methods for detecting hidden hemorrhages:

1. Gregersen's test. A thin layer of feces is applied to a glass slide. Add 2-3 drops of benzidine solution, hydrogen peroxide. A positive reaction is indicated by the appearance of a blue or greenish color. This reaction reveals occult bleeding with blood loss of more than 15 ml per day, but often gives a false positive result (especially if the patient did not adhere to a meat-free diet).
2. Weber test. Filter paper is placed on a glass slide. Feces are smeared on it with a thin layer. 2-3 drops of glacial acetic acid, freshly prepared tincture of guaiac resin, hydrogen peroxide are dripped. In the presence of blood, the color becomes blue-green, purple. A positive reaction occurs only with blood loss exceeding 30 ml per day.
3. Express tests. Use standard paper tests. A layer of feces is applied to the strips impregnated with guaiac resin. Add 2-3 drops of acetic acid and hydrogen peroxide. If the color of the paper turns blue, then the reaction is positive.
4. radioisotope method. Cr51 is added to the patient's heparinized blood. In 30-60 minutes, it penetrates into erythrocytes, combines with globin. Radioactive chromium-labeled erythrocytes retain radioactivity for 24 hours after administration of the composition to the patient. Then the presence of Cr51 in the feces is detected. The degree of radioactivity of the feces indicates hidden hemorrhages. The method is expensive, lengthy, but the most reliable.

All these methods reveal the presence of hidden bleeding. This is not enough for diagnosis. It is necessary to determine where exactly the blood enters the feces.

How to determine the place of bleeding in hidden hemorrhages

To begin with, bleeding from the nasopharynx of the oral cavity is excluded. Consultation of the dermatologist is necessary. This will help to identify syndromes characteristic of other diseases:

• Gardner (steatoma, osteoma, indicative of vasculitis);
• Osler-Randu-Weber (presence of telangiectasias);
• Peitz-Jeghers (characteristic of);
• symptoms.

If hemorrhage from the upper gastrointestinal tract is suspected, the contents of gastric juice are examined.

If there is a high probability of hemorrhages from the intestines, then appoint:

• anoscopy;

Be sure to examine the lymph nodes, if they are enlarged - there is a high probability of a malignant tumor.

A negative reaction to blood in the stool in the presence of other symptoms does not indicate the absence of pathology. The diagnosis is made taking into account the patient's complaints, the results of physical and other studies.

Which doctor to contact

Analysis of feces for occult blood allows early detection of cancer, the presence of other pathologies of the gastrointestinal tract. You can conduct it yourself using special paper tests. When symptoms of diseases of the gastrointestinal tract appear, it is better to contact a gastroenterologist. In the event of intestinal disorders - to the proctologist. They will recommend the best method for determining occult blood in the feces, and prescribe other studies necessary for accurate diagnosis. According to the results, treatment will be prescribed.

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.

A test for occult blood in the feces is prescribed if occult bleeding is suspected. Normally, 1 g of feces of a healthy person contains no more than 2 mg of hemoglobin, that is, less than 2 ml of blood is excreted with feces during the day. With significant gastrointestinal bleeding, the color of the stool changes.

With a high localization of the source of bleeding (stomach, duodenum, small intestine), they become dark, tarry (melena), and with low blood in the feces, it is detected visually. If blood is present in the feces, but is not determined either visually or during microscopy, it is called latent, and the bleeding, respectively, is latent. It can be detected by laboratory methods of fecal occult blood analysis:

• test with benzidine (Gregersen reaction) or guaiac resin;
• quantitative immunochemical method.

Detection of blood in the feces indicates that the patient has diseases of the stomach or intestines that occur with a violation of the integrity of their mucous membrane.

Causes of gastrointestinal bleeding

The following diseases lead to the development of bleeding from the organs of the gastrointestinal tract (GIT):

• peptic ulcer of the stomach and duodenum;
• polyps, benign and malignant tumors of the digestive tract;
• diffuse familial polyposis;

Patients suffering from these diseases should be regularly tested for occult blood in the feces.

After reaching the age of 50, each person is recommended to take a fecal occult blood test annually, it is included in the algorithm for early diagnosis of malignant neoplasms of the intestine, the incidence of which at this age increases significantly. The appearance in adults, especially older than 50 years, of a positive test for fecal occult blood is the basis for further in-depth examination.

Benzidine test

Benzidine test (Gregersen-Adler reaction) is a chemical reaction used to detect blood impurities in biological material (urine, gastric juice, feces). In the presence of blood, after adding the reagent, the color of the test material becomes bright green or blue.

This analysis requires the preparation of the patient, since it is possible to obtain a false positive result due to hemoglobin contained in meat food, some vitamins and other substances.

To exclude a false positive result, you must follow a diet. 72 hours before the study, food of animal origin (fish, poultry, meat) and some vegetables (tomatoes, zucchini, herbs, green apples, horseradish, cucumbers, cauliflower, broccoli) are excluded from the diet.

In infants, the cause of a false positive result may be cracked nipples in the mother. During feeding, these cracks bleed, and the children swallow the secreted blood along with breast milk.

Diet in preparation for the study:

• dairy products (ryazhenka, kefir, cheese, cheese, cottage cheese, milk);
• cereals (oatmeal, rice, millet);
• vegetables (potatoes, carrots, white cabbage);
• fruit;
• weak tea, mineral water without gas;
• sweets and confectionery.

Immunochemical analysis of feces for occult blood

Old methods for determining occult blood in feces, including the benzidine test, react not only to human hemoglobin, but also to animal hemoglobin contained in meat products, so it is not always possible to accurately determine what a positive result shows - occult bleeding or errors nutrition.

The immunochemical method is devoid of this drawback and reacts specifically to human blood. This means that it does not require the patient to follow a special diet.

Rules for collecting material for occult blood testing

Three days before the test, you should stop taking iron and bismuth preparations, and one day - vitamin C (ascorbic acid) and Aspirin (acetylsalicylic acid).

72 hours before the study, it is necessary to exclude any diagnostic or therapeutic manipulations affecting the organs of the gastrointestinal tract, that is, colonoscopy, sigmoidoscopy, X-ray contrast examination of the digestive tract should not be performed.

The day before the fecal occult blood test, the patient is not recommended to brush his teeth, as a brush, especially with hard bristles, can injure the gums, causing them to bleed.

Feces for research should be taken only after self-defecation. It is unacceptable to take laxatives or enema before the study, as this distorts the result.

With a high localization of the source of bleeding, the feces become dark, tarry in color, and with a low localization, blood in the feces is detected visually.

Care must be taken to prevent urine or vaginal discharge from entering the material by urinating before defecation, then washing and drying the perineum with a towel. During bowel movements, you should not strain excessively.

Immediately after defecation, material is taken from 3-4 areas of stool and placed in a disposable container with a lid and a spatula, which is obtained in advance from the laboratory or purchased from a pharmacy. 1/3 of the container is enough for research. The collected material must be delivered to the laboratory as soon as possible.

Deciphering the analysis of feces for occult blood

Normally, blood should not be detected in the feces. The following factors can lead to false results:

• non-compliance by the patient with the prescribed diet (when setting a benzidine test);
• collection of analysis on the days of menstruation in women;
• high bleeding gums.

In infants, the cause of a false positive result may be cracked nipples in the mother. During feeding, these cracks bleed, and the children swallow the secreted blood along with breast milk.

The immunochemical method can also give false negative results. This is observed in cases where fresh unchanged red blood cells are present in the feces, for example, with bleeding anal fissures or external hemorrhoids.

If all the rules for preparing and collecting a fecal occult blood test were followed, and factors affecting its reliability were excluded, the detection of blood in it indicates that the patient has diseases of the stomach or intestines that occur with a violation of the integrity of their mucous membrane:

• nonspecific ulcerative colitis;
• Crohn's disease;
• colorectal carcinoma;
• peptic ulcer of the stomach or duodenum;
• intestinal tuberculosis;
• haemorrhoids.

If there is doubt about the reliability of the results of the analysis, it is done again.

Video from YouTube on the topic of the article: