How to collect stool for occult blood. Examination of feces for occult blood

Fecal occult blood testing is widely used to diagnose bleeding in the gastrointestinal tract. If the preparation is incorrect or the material is collected incorrectly, 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 stool

The main and most common cause of occult blood in the stool is tumor processes in the intestines (colorectal cancer). Hidden blood in stool is that which is not visible visually or even under a microscope. It is known that intestinal tumors bleed. There is a small amount of this blood in the initial stages of the disease. Once in the intestinal lumen, red blood cells and along with them hemoglobin are destroyed by digestive enzymes and therefore become invisible.

In addition to colorectal cancer, the causes of the appearance of occult blood in the stool of 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).

Why is research needed?

A stool occult blood test shows the presence of 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. In what cases is a stool test for occult blood indicated? Below are the main factors:

• Pain or discomfort during or before bowel movements.
• Any impurities in stool (mucus, foam).
• Changes in stool character. It has become liquid or, on the contrary, too dense.
• Traces of blood are periodically visible in the stool.
• Decreased appetite or significant weight loss.
• Abdominal pain of any location.
• The presence of symptoms such as heartburn, nausea, vomiting, iron taste in the mouth.
• Periodic causeless increase in body temperature.
• Annually as a screening examination for patients over 40 years of age. It is carried out for the early detection of colon tumors.

If you have any of the above symptoms, it is recommended to have your stool tested for occult blood.

Preparing for a stool occult blood test, what is it for?

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


Today there is an analysis that does not require special preparation of the patient. This is an immunochemical stool 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 intestines (colon and rectum). In the upper sections, hemoglobin is significantly affected by digestive enzymes and is destroyed. Therefore, after the study, if the result is positive, it is recommended to undergo additional examination (colonoscopy, for example).

How to prepare for the analysis?

1. Diet before stool occult blood test. For three days (72 hours) you need to exclude food of animal origin (meat, fish) from your 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 medications, bismuth and barium sulfate is not recommended. Also, on the eve of the test, you should not take acetisalicylic 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 study, sigmoidoscopy, colonoscopy).
4. You should not use laxatives or give enemas. Material for analysis is collected after three spontaneous bowel movements from different areas of the stool.
5. This test is not recommended for menstruating women.

How to get tested correctly?

For a reliable result, after proper preparation, you need to collect the feces in a specially designed container purchased at the 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.

Decoding the analysis results

A positive test reaction indicates processes in the intestine that lead to a violation of the integrity of its mucous membrane. This means that red blood cells and hemoglobin enter the intestinal lumen. But you should 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, ulcerative lesions of the esophagus, hemorrhoids and even helminths. To make an accurate diagnosis, a complete examination of the patient is necessary.

The test result may also be false positive if a reaction occurs not to human hemoglobin, but to substances or dyes contained in food. This usually happens when the patient is incorrectly or insufficiently prepared for the study. In any case, a positive result is a reason for a more in-depth examination of the patient.

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

– laboratory examination of stool aimed at identifying hemoglobin. The fecal hemoglobin test is performed as a screening for minor internal bleeding. Determination of occult blood in feces is used to diagnose pathological processes in the gastrointestinal tract, with varicose veins of the esophagus, intestinal polyps, gastric and duodenal ulcers or hemorrhagic syndrome. For analysis, feces are collected in a sealed container. The most common research methods are immunochemical or guaiac test. In healthy adults, a stool occult blood test should be negative. The duration of the study ranges from 1 to 4 working days, depending on the method. In total, 449 addresses were found in Moscow where this analysis could be done.

– laboratory examination of stool aimed at identifying hemoglobin. The fecal hemoglobin test is performed as a screening for minor internal bleeding. Determination of occult blood in feces is used to diagnose pathological processes in the gastrointestinal tract, with varicose veins of the esophagus, intestinal polyps, gastric and duodenal ulcers or hemorrhagic syndrome. For analysis, feces are collected in a sealed container. The most common research methods are immunochemical or guaiac test. In healthy adults, a stool occult blood test should be negative. The duration of the study ranges from 1 to 4 working days, depending on the method.

Fecal occult blood testing is considered a "laboratory alternative" to colonoscopy. If a patient has severe bleeding from some part of the gastrointestinal tract, then first of all the color of the stool changes, which can be determined even by eye. If there is bleeding from the lower intestine (such as the rectum), the blood in the stool will be bright red. When the upper gastrointestinal tract (esophagus, stomach or small intestine) bleeds, the stool becomes tarry. In this situation, the patient should be provided with urgent medical care. If minor bleeding occurs due to injury to the gastrointestinal mucosa, the coloring and consistency of the stool do not change, and red blood cells are determined during microscopy. If microscopic examination does not reveal red blood cells, and symptoms indicate the presence of hidden bleeding, then a stool test for occult blood is required.

With regular use of this test, the detection of late-stage malignant colon tumors is reduced by 45%. In healthy patients, no more than 0.5 ml of blood per day can normally be excreted in the stool. Fecal hemoglobin usually does not lead to changes in the color of stool and is not detected by macroscopic methods. When bleeding is less than 45 ml, the fecal occult blood test becomes positive, so the test is performed to diagnose polyps, ulcers, diverticula or tumors of the gastrointestinal tract at an early stage. This test is widely used in gastroenterology, proctology and oncology to determine pathological processes in the gastrointestinal tract.

Indications

A fecal occult blood test is prescribed during a medical examination (preferably once every 2 years for patients of pre-retirement age), if a tumor is suspected, as well as for people suffering from helminthiasis, polyposis, gastric erosion or ulcerative colitis. If a neoplasm of the gastrointestinal tract (benign or malignant) is diagnosed using an instrumental method, then the patient is advised to test stool for occult blood to exclude minor bleeding. Symptoms for which a study is prescribed include discomfort during bowel movements and false urges, intestinal dyspepsia, abdominal pain, diarrhea, sudden weight loss, restless sleep, weakness, fever, changes in the structure of stool, the presence of foam and mucus in the feces. Hidden bleeding often manifests itself as clinical symptoms of hypochromic or microcytic anemia, therefore, if there are signs of anemia, not only an instrumental examination (gastroscopy and colonoscopy) should be performed, but also a stool test for occult blood.

Preparing for analysis

Collection of stool for analysis of occult blood is carried out in the morning (in women no earlier than the 7th day of the monthly cycle). Before collecting biomaterial, it is important to stop taking iron-containing drugs, bismuth, anticoagulants and laxatives for several days. It is not recommended to do an enema before the test. A fecal occult blood test is carried out 1-3 days before instrumental studies (sigmoidoscopy, irrigoscopy or colonoscopy). 12 hours before collecting feces, it is important to adhere to a special diet - exclude liver, meat dishes and iron-containing foods (peppers, apples, greens, beans). You can eat buckwheat, rice porridge, potatoes, butter, bread, and dairy products. It is important to deliver the container with feces to the laboratory immediately after collecting the biomaterial. Storage in the refrigerator (at temperatures from +4 to +8 0 C) for several hours is allowed. Feces are collected after spontaneous defecation, and it is important to ensure that no urine gets into the container (feces are collected from 3 different places).

To detect fecal hemoglobin, an immunochemical test or benzidine and guaiac tests are used. With the guaiac method, feces are applied to paper, after which hydrogen peroxide and a guaiac reagent are added. The principle of testing samples is that heme in hemoglobin manifests itself as a peroxide (it instantly destroys the structure of hydrogen peroxide). As a result, benzidine or guaiac (depending on what is used) quickly oxidizes and turns a different color. If there are traces of blood in the feces, the paper changes color within a few seconds.

The immunochemical fecal occult blood test uses antibodies to intact human globin and hemoglobin. The advantage of this technique is considered to be increased specificity and sensitivity (98-99%) in the diagnosis of bleeding in the rectum and colon. However, the immunochemical test is not sensitive to bleeding from the upper gastrointestinal tract, where globin is quickly digested, so in this case the guaiac test is predominantly used. The period for performing a stool occult blood test is from 1 to 4 days, depending on the chosen method.

Normal values

Normally, in healthy people, hemoglobin is absent in the analysis of stool. When quantitatively determined, a negative result is from 0 to 50 ng/milliliter. Repeated testing is sometimes required to confirm reference values. The absence of hidden blood in the stool does not 100% exclude the presence of ulcers or neoplasms of the gastrointestinal tract in the patient, so it is important that the test results are evaluated together with other studies.

Positive result

The main reason for a positive fecal reaction to occult blood is considered to be a violation of the integrity of the gastrointestinal mucosa and the development of minor bleeding in patients due to injuries to the nasal mucosa,

> Examination of feces for occult blood

This information cannot be used for self-medication!
Consultation with a specialist is required!

“Hidden” is called blood that is not detected visually or microscopically in the stool. To detect it, a special laboratory method is used - testing stool for occult blood (benzidine test). With its help, hemoglobin is detected in feces, which is released when red blood cells are destroyed. A chemical added to a stool sample reacts with hemoglobin. This changes the color of the stool. The amount of blood in the stool is judged by the speed at which the color appears and its intensity.

When is the test scheduled?

The analysis is used to diagnose hidden bleeding from the gastrointestinal tract and to clarify the type of anemia. Bleeding is a sign of many serious diseases of various parts of the gastrointestinal tract - Crohn's disease, tuberculosis and intestinal tumors, ulcerative colitis, gastric or duodenal ulcers. Anemia, abdominal pain, sudden weight loss, lack of appetite, false urge to defecate, discomfort in the rectum, heartburn, nausea, vomiting, persistent constipation or frequent pasty stools - all these symptoms give the doctor reason to prescribe a stool test for occult blood. Bleeding can be an early sign of colon cancer, so it is recommended that all people aged 50–75 years have a stool occult blood test once a year.

Which specialist prescribes the test, and where can it be taken?

The analysis is prescribed by a therapist, gastroenterologist, general practitioner, oncologist or surgeon. It can be taken at a clinic at your place of residence, at a private medical center or a paid laboratory.

Preparing for the study

The chemical reagent used to conduct the study reacts to the presence of even the smallest amount of hemoglobin, including that contained in the meat (in the red blood cells of the animal) eaten by the subject the day before. Therefore, you need to carefully prepare for the test. For three days before collecting feces, you must follow a diet: exclude meat, offal, fish, and green vegetables from the diet. It is not allowed to eat tomatoes, white beans, spinach, bell peppers, horseradish, beets, apples, pomegranates, and blueberries. For the same period, you need to discontinue medications that change the color of stool (iron, bismuth preparations), and eliminate the use of rectal suppositories and oils. The study can be done no earlier than three days after an X-ray of the abdominal cavity with barium; for women - no earlier than three days after menstruation.

How to collect stool for research?

Feces are collected from several (3–4) places of freshly excreted feces. The container used is a disposable plastic container with a tight-fitting lid. For research, 10–15 g of feces is sufficient. They should not contain any impurities, including urine. Stool should not be sent for analysis after an enema, administration of Vaseline or castor oil, or rectal suppositories. It is not allowed to bring feces in diapers or matchboxes to the laboratory. To obtain accurate results, it is recommended to store the resulting material in the refrigerator. It should be delivered to the laboratory within three hours after collection.

Decoding the analysis results

Normally, the test result will be negative. The presence of blood in the stool is designated as a positive reaction. The laboratory gives the result of the study in qualitative terms: “+” - a weakly positive reaction, “++” and “+++” - positive, “++++” - a strongly positive reaction. A positive reaction does not always mean that a person has gastrointestinal bleeding. The reasons for the appearance of blood in feces can be bleeding from the nose, pharynx, gums, hemorrhoids, improper preparation for the test, etc. Therefore, the results of the analysis are evaluated only in conjunction with data from other research methods.

Blood found in feces almost always means the development of a disease in the gastrointestinal tract. Therefore, if it is not detected in a timely manner, it can lead to serious complications. It is worth noting that the smallest particles in blood stool cannot be detected with the naked eye. But they are the main indicator of the development of a pathological process in the gastrointestinal tract. A laboratory test for occult blood will help identify microscopic blood in the stool.

It is carried out by taking biological material from the patient and further examining it. This diagnostic method requires careful and consistent preparation, otherwise the results will be false positive, which will prevent the correct diagnosis.

We will learn further about what the test for occult blood in the stool reveals, how to prepare for it, and in what cases doctors prescribe the test.

Testing for occult blood in stool is carried out in three ways.

Only a doctor should determine what type of research should be performed, depending on the specific case.

The reaction with benzidine is used quite rarely in modern medicine. This type of study can detect only 15 ml of blood in excrement. In addition, this diagnosis is characterized by multiple false results.

Attention! Immunochemical tests for the development of oncology in the large intestine are positive in 98% of cases. In the presence of polyposis in the intestines - 60%. Thanks to this diagnostic method, doctors are able to diagnose colon cancer at an early stage, which can reduce mortality from this disease by 25%.

Why does occult blood appear in stool?

The main source of blood excretion in feces is cancer developing in the small or large intestine. At the same time, the forming hemoglobin and red blood cells do not turn red and cannot be detected, even by performing a coprogram.

This is explained by the fact that malignant tumors at the primary stage of development are small in size. When feces move through the intestinal passage, the formation may be slightly injured, releasing a small amount of blood, which penetrates the intestinal duct and is processed by bacterial or digestive enzymes. This process causes the blood to lose its natural color and become transparent. Therefore, no test other than testing for blood hidden in feces will be able to detect it.

What other diseases can be identified using this study?

Reasons for the presence of occult blood in the stool in children under 3 years of age.

Important! If the results are positive, a repeat test is required. After all, quite often patients violate the preparatory stage, characterized by adherence to a strict diet.

When is a test needed to determine the presence of occult blood in the stool?

The main indication for this study is the patient’s complaints of abdominal pain and general malaise. A gastroenterologist almost always prescribes this testing in order to detect malignant and benign processes in the gastrointestinal tract at the initial stage of their development.

What other symptoms are an indication for testing to detect the presence of occult blood in excrement?

1. Soreness, colic, bloating, which immediately disappear after bowel movement.
2. Pain during the act of defecation at the time of straining.
3. A feeling of insufficient emptying of the intestines from feces after bowel movement.
4. Reluctance to eat.
5. Dramatic weight loss.
6. Detection of bloody impurities and mucus in the stool.
7. Often troublesome diarrhea or constipation.
8. Complaints of nausea, vomiting, increased temperature.

Attention! It is recommended to take a test once a year to determine occult blood in feces up to 40 years of age to exclude the development of tumors - malignant and benign.

Preparatory stage

Any study can give false results due to improper preparation for its conduct. Here are the basic rules that will allow you to get the most reliable result.

To take the test, you need to purchase a special sterile container with a plastic spatula from the pharmacy. Parts of excrement are taken from different areas and placed in a container. The biological material is sent to the laboratory within 3 hours.

Important! Many paid laboratories practice stool examination after 3 systematic bowel movements. Each time, excrement particles are taken from different places.

Video - Fecal occult blood test

What the analysis shows

A small amount of blood in the stool is absolutely normal. A small amount of it is always found in feces - 1 ml (1 mg of hemoglobin per 1 g of feces). However, this indicator is considered normal if the specified volume is excreted in excrement per day. No one will pay attention to such a tiny amount of attention, since no one has yet canceled the natural processes in the body.

A positive reaction in the analysis results is marked with a “+” sign. And the more of these marks, the higher the intensity of the reaction. A strongly positive result looks like this: “++++”, a weakly positive reaction – “+”, a positive reaction – “++” or “+++”.

Important! If the reaction turns out to be negative, this does not mean that there is no internal bleeding. After all, this process is periodic. Therefore, they are not always identified during testing.

False positive and false negative reaction

To get the most reliable results, you should follow a nutritious diet. The preparatory stage requires a careful approach, otherwise the analysis will show incorrect results, which will complicate the diagnosis.

If you neglect medical rules, then hemoglobin levels in the absence of gastric or intestinal bleeding will be high. Thus, the reaction with benzidine has increased sensitivity to iron. And if the patient eats at least one green apple on the eve of the test, this will certainly lead to a false positive result.

Laboratory analysis of stool to determine occult blood helps to recognize gastrointestinal diseases, including malignant processes, at the initial stage of their development. This test is used when conventional research methods are powerless.

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 stool test for occult blood! 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 and genitourinary system.

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

When is a stool occult blood test prescribed?

At the doctor's appointment, the abdominal cavity and the internal organs located in it will be examined. After the 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 test is prescribed if the doctor suspects bleeding in one of the parts of the digestive tract. Analysis is prescribed if the following factors occur:

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

With intense bleeding in any part of the gastrointestinal tract, the blood changes the appearance of the stool quite significantly, which becomes noticeable to the naked eye. If bleeding occurs in the upper sections, the stool becomes black and tar-like due to the interaction of the blood with local enzymes.

Video

If there is bleeding in the lower parts of the gastrointestinal tract, then scarlet blood (its clots) can be clearly visible in the stool.

One of the main causes of constipation and diarrhea is use of various medications. To improve bowel function after taking medications, you need to do it every day. drink a simple remedy ...

Why is research needed?

If there is a suspicion of bleeding in any part of the gastrointestinal tract, doctors immediately prescribe stool tests to the patient.

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

In most cases, internal bleeding in the organs of the gastrointestinal tract may be intermittent and light, traces of it will not be noticeable in the stool. If the doctor suspects its presence, he will prescribe a stool test for occult blood.

This test 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 through the interaction of the test stool and special chemicals (reagents), which change their color as a result of the reaction.

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

A stool occult blood test allows you 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.

Preparing for analysis

If a patient has been scheduled for a stool occult blood test, he or she must follow certain instructions.

Compliance with these rules directly affects the condition and composition of the research material (stool), on which the accuracy and reliability of diagnostic results depends.

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

About ten days before collecting stool, you should stop taking aspirin, non-steroidal anti-inflammatory drugs and other analgesics. It is worth stopping taking various laxatives and medications that contain bismuth and iron.

It is important to note that if the patient has been prescribed a diagnosis using x-rays, then stool should be collected at least two to three days after the x-ray.

A fairly large number of doctors strongly do not recommend brushing your teeth before bowel movements in order to avoid the possible entry of blood from the gums or teeth into the gastrointestinal tract.

What can you eat before the test?

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 required balance of fats, proteins and carbohydrates in food will help you get the right conclusion.

The most common diets in this case are the Schmidt or Pevsner diets.

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

You should stop eating vegetables and fruits that contain catalase (an enzyme).

How many days does it take?

Preparing for analysis may 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 a stool 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 assemble a chair correctly?

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.

The most important– 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 traditional, is contraindicated.

Study material is collected after at least three consecutive bowel movements.

It is important to take into account that feces are collected from various parts of the feces. Do not allow urine and feces to mix.

If possible, collected stool 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 to be tested for hidden bleeding. Analysis results can be ready the next day.

Decoding the analysis results

The result of the obtained stool analysis for hidden bleeding determines all further actions of both 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 feces contain substances that the stomach is not able to digest.

A negative result may indicate the presence of polyps in the patient's colon, which raises the possibility of colorectal cancer progression.

The problem with stool testing for hidden bleeding is that it cannot always show the presence of polyps in the intestines. If the doctor has suspicions about this, he may prescribe additional diagnostics.

A positive result means that bleeding is present in the gastrointestinal tract. 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 intestinal walls);
8. colorectal cancer;
9. erosive esophagitis (inflammation of the esophagus affecting its mucous membrane).

It is worth considering that the result of a stool occult blood test may be false positive. The reasons for this may be nosebleeds and dental bleeding. In women, the presence of blood in the stool can be caused by radiation after cancer of the genital organs, or vaginal varicose veins in the last days of pregnancy.

Quite often, the result of this examination 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 stool occult blood test is prescribed directly by the attending physician. That is why it is done in the clinic where the patient is registered. The test can be taken at various medical centers. For the convenience of the patient, a blood test for hidden bleeding can be done in a specialized laboratory at any time convenient for him. Many people take several tests simultaneously to different laboratories to obtain a more accurate and reliable result.

Prices

The price of the test varies depending on the medical institution where you do it. Taking the test at the clinic at your place of registration is absolutely free.

You will only have to spend money on a plastic container for collecting biological material. Tests in medical centers and laboratories are paid. On average the price is about 130 hryvnia in Ukraine and 300-400 rubles in Russia.