If the occult blood test is positive. How to test feces for occult blood correctly

Express test for occult blood in feces allows to detect the presence of hidden bleeding, with a sensitivity of 2 mg of hemoglobin per 100 ml of water. This allows you to determine at home the presence of bleeding into the intestinal lumen that is not detectable by the eye.

The most effective and reliable test is produced by the American company “Biomerica” - "EZ Detect". The chromophilic dye tetramethylbenzidine is applied to the test strip; when it comes in contact with hemoglobin, its color changes. At the same time, the cross-shaped window changes color to blue or green. This test can only be ordered through online stores.

There is a domestic budget analogue, which is not as accurate, but it can be purchased at almost all pharmacies. This test is produced by the Med-Express Diagnostics company under the name "Rest assured".

You can also purchase on domestic markets Cito Test FOB to detect hidden blood in stool. The company specializes in express diagnostics oncological pathology, so the test can be trusted.

Table 1. List of rapid tests for the presence of occult blood in potassium

What diseases can it detect?

• – most common reason the appearance of occult blood;
• – a benign disease, which can also cause hidden bleeding when the polyp is microtraumatized by chyme;
• – bleeding is often obvious;
• – often clinically manifested by the presence of blood streaks in the stool.

The test only determines the presence of blood, specific disease can only be identified through examination - and others.

• over 40 years of age, especially those with bad habits(alcoholism, smoking);
• with a family history of colon cancer;
• with metabolic syndrome ( abdominal type obesity);
• with a sedentary lifestyle (office workers, drivers vehicles etc.);
• with impaired stool with a tendency to constipation;
• with precancerous intestinal diseases (polyposis, autoimmune inflammatory diseases and so on).

Preparing and conducting the test

The following points should be kept in mind before taking the test:

The test is carried out as follows:

1. Unscrew the collection cap.
2. Remove the applicator.
3. Make sure that the reagent inside the collection does not spill.
4. Immerse the applicator in 3-5 areas of the stool being analyzed.
5. Remove excess feces from the surface of the applicator with a dry cloth.
6. Place the applicator into the collection containing the reagent.
7. Shake the collection vigorously to evenly mix the stool with the reagent.
8. Open the tablet along the slot.
9. Place on a flat, dry surface with the test area facing up.
10. Turn the collection over.
11. Unscrew the cap (pin-plug).
12. Place 2 drops of reagent onto the window of the test plate.
13. Wait 5 minutes before assessing the result.

Decoding

Test positive

The appearance of two colored stripes in the test system window. Any intensity of color indicates that there is hidden blood in the stool; the intensity of the color depends on the amount of hemoglobin.

After receiving a positive result, you must urgently consult a doctor for further examination: blood tests, irrigography, colonoscopy and other studies at the discretion of the doctor. The sooner cancer is tested and treated, the greater the likelihood of a successful outcome and increased survival.

Test negative

Only one line in control area C is colored, test strip T remains clear.

If the test was carried out as a screening diagnosis in the presence of clinical manifestations, it is better to contact a specialist and undergo more precise research (see) to determine the causes of complaints. If the test was carried out as an annual screening examination (like fluorography) after 40 years, then the test can be repeated a year later.

Conclusions

World practice states that the effectiveness of this test is undeniable. Errors may occur, more precise research for diagnosing colon cancer in the initial stages is.

If there are clinical manifestations and complaints, you should consult a doctor. The specialist himself may recommend a rapid test for occult blood as a screening. The earlier the diagnosis is made, the more likely it is to receive timely and effective treatment.

General information about the study

Analysis of feces for occult blood is an extremely important laboratory test in the diagnosis of hidden bleeding from various parts of the gastrointestinal tract. Such bleeding is one of the early symptoms a whole series serious illnesses Gastrointestinal tract, including oncological ones. With hidden bleeding, even long-term, it is very difficult to determine the presence of blood in the stool, both visually and microscopically, and most often simply impossible.

At heavy bleeding from various parts of the gastrointestinal tract, the blood changes so much appearance stool that its presence can often be determined visually. If the bleeding is from the lower intestines (colon, rectum), the blood will be scarlet in color, possibly in the form of clots or impurities. If the source of bleeding is in the upper gastrointestinal tract (part small intestine, esophagus, stomach), then the feces turn into black, “tarry” due to the interaction of blood and special enzymes produced in these parts of the gastrointestinal tract. As a rule, if there are visual signs Gastrointestinal bleeding, then the situation is acute and requires emergency measures (emergency care). However, with less pronounced violations the integrity of the gastrointestinal mucosa, with the involvement of a small number of vessels in the process, the color and consistency of stool do not change, but red blood cells in the stool will be visible during microscopic examination. If red blood cells are not visible microscopically, but there is a suspicion of hidden bleeding, then a stool test for occult blood is required. This study carried out by measuring the amount of changed hemoglobin (and not the red blood cells themselves).

A positive stool reaction to occult blood means that the person has a disease gastrointestinal tract, causing disruption of the integrity of the mucosa when a small amount of blood is released into the lumen of the stomach or intestines. This can occur with stomach or duodenal ulcers, nonspecific ulcers, Crohn's disease, polyps, and helminth infestations. Since tumors, primary and metastatic, cause damage to the gastrointestinal mucosa even if they are small in size, the study is used at the first stage of identifying gastrointestinal tumors. The determination of occult blood is especially important when diagnosing colon cancer, since it is with tumors in this part of the intestine that occult bleeding begins in the earliest stages.

Blood in the stool can also be detected during nosebleeds, bleeding from the gums and pharynx, in patients with varicose veins of the esophagus, erosive esophagitis, hemorrhoids and other diseases, so this must be taken into account when assessing the results of the analysis.

The reliability of the analysis is highest when it is repeated. Negative test results do not rule out possible availability a patient with erosive-ulcerative or tumor lesions of the gastrointestinal tract. It is important that the results should be assessed in conjunction with other instrumental and laboratory studies, since they themselves cannot be the only criterion for making a diagnosis.

Sometimes all stool tests for occult blood are mistakenly called the Gregersen test or Gregersen test, erroneously because the Gregersen test (benzidine test) is the most common, but not the only method for detecting occult blood in feces, urine, vomit, etc.

What is the research used for?

• For the diagnosis of gastrointestinal diseases accompanied by violations of the integrity of the mucous membrane (peptic ulcer of the stomach and duodenum, primary and metastatic tumors of the esophagus, stomach, large and small intestines, duodenal papilla, intestinal tuberculosis, ulcerative colitis, helminthiases).
• To assess the degree of damage to the gastrointestinal mucosa.
• To assess the adequacy of therapy peptic ulcer stomach, UC, Crohn's disease, intestinal tuberculosis.
• To assess the severity of gastrointestinal disease and give its prognosis.

When is the study scheduled?

• For abdominal pain, heartburn,...
• With frequent pasty stools, false urge to defecate, weight loss, loss of appetite, increased body temperature.
• In case of identified tumors of the gastrointestinal tract (instrumental methods) to exclude hidden bleeding of the gastrointestinal tract.
• If helminths are detected, to assess damage to the gastrointestinal mucosa.
• If the patient has previously been diagnosed with a stomach ulcer (ulcerative colitis, Crohn's disease, polyposis, intestinal tuberculosis).

– laboratory test 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, when varicose veins esophageal veins, 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 the patient has opened heavy 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.

When this test is carried out regularly, the detection of malignant tumors of the large intestine on last stage decreases 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 stool test for occult blood becomes positive, so the test is carried out to diagnose polyps, ulcers, diverticula or tumors of the gastrointestinal tract on initial 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 instrumental method If a neoplasm of the gastrointestinal tract (benign or malignant) is diagnosed, the patient is advised to test stool for occult blood to exclude minor bleeding. Symptoms for which testing is ordered 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 appears clinical symptoms hypochromic or microcytic anemia, therefore, if there are signs of anemia, not only instrumental examination(gastroscopy and colonoscopy), but also a stool test for occult blood.

Preparing for analysis

Collection of stool for occult blood testing is carried out in morning time(for women no earlier than 7 days 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 stool occult blood test is performed 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, 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 area of ​​direct and colon. However, the immunochemical test is not sensitive to bleeding from upper sections Gastrointestinal tract, where globin is quickly digested, therefore in this case it is used predominantly guaiac test. 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 mucous membrane of the gastrointestinal tract and the development of minor bleeding in patients due to injuries to the nasal mucosa, stomatitis, periodontal disease, gastric ulcers, UC, hemorrhoids, erosive esophagitis or intestinal tuberculosis. Primary and secondary neoplasms, colon cancer cause bleeding and inflammation of the gastric and intestinal mucosa in the first stage of the disease, so these pathologies are also the cause of a positive reaction in the stool test for occult blood. The vascular network on the surface of a malignant tumor of the small intestine or colon polyp has a fragile structure and is therefore easily injured during defecation. In this case, a small amount of blood enters the stool, which cannot be visually determined.

Treatment of abnormalities

Fecal occult blood testing is considered common medical research, thanks to which it is possible to diagnose bleeding from different segments of the gastrointestinal tract, including tumor processes on initial stage. When you receive test results, it is important to contact your healthcare professional immediately:

Normal in stool there shouldn't be any blood, but there are some pathological conditions, in which such a phenomenon is considered one of the characteristic signs.

Hidden blood is a specific condition in which bloody masses in the stool are not visible to the naked eye, even under a microscope, however, with a deeper study of the biomaterial, the presence of blood is revealed.

Types of stool tests for occult blood

A variety of tests and screenings are used to detect blood in stool. Today, laboratories use the 2 most informative methods to detect occult blood:

• Immunochemical test. Such diagnostics are usually prescribed to identify pathological processes in the lower sections digestive system. The reaction occurs only in the presence of human hemoglobin, so it makes no sense for patients to adhere to any dietary restrictions, for example, to refuse to eat meat and iron-rich foods before diagnosis. Such a diagnosis is more convenient and is usually used as a screening procedure for the subject.
• Gregersen reaction or benzidine test. This test is performed chemically and is used to detect bleeding in all structures of the gastrointestinal tract. Such testing is sensitive not only to human hemoglobin, but also to animal sources of iron, so a strict diet that excludes the consumption of meat products is necessary before diagnosis.

An immunochemical test for occult blood is considered the most informative; however, it is not able to detect bleeding when it is localized in the stomach or esophagus.

Only a specialist decides which research method is most appropriate in the case of a particular patient, so you need to contact a doctor with this question, and only then go to the laboratory to take a sample.

Indications

Typically, the need for analysis arises when there are suspicious symptoms such as:

1. Painful syndrome in the abdominal area;
2. Frequent diarrhea and constantly liquefied stool;
3. Dyspeptic symptoms such as nausea, bloating or heartburn, disturbing for a long time;
4. Various digestive disorders;
5. Sudden causeless weight loss;
6. Clinical examination of stool does not show bleeding.

In addition, test screening for occult blood is carried out if there is a suspicion of colorectal oncology, anemia of unknown etiology, to detect intestinal bleeding and for preventive purposes in patients over 50.

If they are visible without any instruments or research, then this indicates their abundance. An experienced gastroenterologist can determine by the shade of stool where the bleeding focus is located.

If there are bright spots of blood in the stool, this indicates damage to the rectum or large intestine. If the stool has a black tint, the causes of bleeding should be looked for in the stomach or tissues of the esophagus.

Preparation

For maximum reliability of the test for occult blood, it is necessary to properly prepare for the diagnosis.

The main requirement for patients undergoing testing for the Gregersen reaction is to follow dietary recommendations.

Why should you exclude fish and meat dishes, seafood, alcohol, a few days before the study? vitamin preparations and reception medicines, containing iron, which have analgesic and anti-inflammatory effects.

IN the latter case the ban is due to the presence of ibuprofen or aspirin in these drugs. Also, the purpose of the diet is to normalize stool so that it becomes natural without the use of any drugs that may distort the result.

Ladies during menstruation should approach such a study with special care, because if menstrual fluid penetrates into the feces, the reaction will show an incorrect result.

You should stop using it about a week before the test. rectal suppositories, oil compresses or microenemas.

You need to be especially careful when brushing your teeth so as not to damage the gums, otherwise blood may penetrate the gastrointestinal tract and appear in the samples during the study, which will lead to an erroneous result.

How to assemble?

The collection of biomaterial is also important for reliability. The feces intended for analysis should not contain any foreign impurities such as urine, water, secretions, etc.

Therefore, it is better to purchase a sterile container from a pharmacy for feces. The potty or vessel will also need to be disinfected. You cannot collect feces from the toilet.

Only natural stool without enemas or laxatives is suitable for the laboratory sample. Urine should not get into the container with feces.

Using a special spoon, you need to transfer the biomaterial into a container. By volume, feces should occupy at least 1/3 of the container. It is better to put several different fractions of feces, then the result will be more accurate.

How to submit?

After collecting stool, you need to send it to the laboratory as soon as possible. possible time storage – 3 hours.

There is no need to preserve or freeze stool; such samples are not suitable for diagnosis.

If stool has been collected, but it is not possible to deliver it to the laboratory right now, then you can place it in a refrigerator. But storing the sample for more than 3 hours is unacceptable.

What does the study show?

Therefore, any method for detecting rectal blood will show its presence. This is a consequence of natural processes, so doctors do not react to such indicators, paying attention only to higher indicators.

The intensity of the reaction is shown by the number of plus signs. If the result is weakly positive, then the analysis is assessed with one plus sign - “+”, a strongly positive result looks like “++++”.

Negative test results are the norm, but such data do not always indicate the absence of hidden internal bleeding. Sometimes bleeding is periodic, so it is not always detected during test screening.

When is the result positive?

At positive result the doctor concludes that there is much more blood in the stool than is allowed naturally. And this may indicate the development of pathologies such as:

• Infectious processes provoked by Koch's bacillus;
• Inflammatory lesions of the duodenum or;
• Tuberculosis;
• Periodontal disease or stomatitis, gum bleeding or periodontitis;
• Ulcerative colitis;
• Cracks in the intestine;
• Acute inflammation of hemorrhoids;
• Varicose veins or thrombophlebitis of the esophagus;
• Nasopharyngeal bleeding.

Also, hidden fecal blood can be a consequence of nasopharyngeal or throat pathologies. Gum bleeding, vasodilatation in the nose and resulting bleeding can all lead to rectal occult blood.

If the patient positive reaction for fecal blood, then he is usually prescribed a repeat diagnosis, because no one has canceled the false results. After all, not all patients approach preparation responsibly, violating the doctor’s recommendations.

How long does the examination take?

Results in the laboratory are prepared within several days, usually 3-6 days. The exact time of diagnosis depends on the specific laboratory.

Price

The average cost of diagnostics for occult rectal blood is about 240-900 rubles, which depends on the specific technique and laboratory.

For convenience, today pharmacies have home tests that operate on the immunochromatographic principle and react to human hemoglobin in stool.

The cost of such a test system is about 250 rubles, and the reliability is more than 99%.

Testing for fecal hemoglobin is a very common diagnostic studies, which allow early stages identify the most dangerous pathological conditions, including oncology. As a result, the patient receives timely treatment, which maximizes the chances of final recovery.

Video about fecal occult blood testing:

Gastrointestinal bleeding can turn out very tragic if it is not detected in a timely manner. In the case of pronounced red stool, doctors have no doubt about the presence of internal pathological processes, but some diseases are almost asymptomatic.

And only the smallest particles of blood in the stool act as a sign of a disorder in the gastrointestinal tract. Conducting such a study requires compliance with a number of rules to exclude false results.

Types of stool occult blood tests

Damage to digestive tract can be localized in both the upper and lower sections. If bleeding occurs in the stomach or duodenum, then the stool becomes dark red, and in the large intestine it becomes bright red.

But not every disorder causes such stool. Often, small ulcers and inflammations only bleed occasionally. There are known cases of tumor development the only symptom of which only a small admixture of hemoglobin appears in the stool.

Laboratory testing makes it possible to determine the presence of blood in the intestines. Analyzes are carried out in two ways:

1. Gregersen method (benzidine test).
2. Immunochemical method.

Gregersen method shows the presence of hemoglobin even at very low concentrations. This is both an advantage and a disadvantage of the analysis. In the presence of benzodine, the iron of the transport molecule is oxidized by hydrogen peroxide and turns blue.

The reaction occurs to hemoglobin, both human and foreign (contained in meat products). Therefore, to clarify the results, doctors often resort to the second method.

Immunochemical analysis kala is more accurate. It is based on the specific effect of antigens on antibodies characteristic of a particular person. The method is usually used when infectious diseases, but this does not affect the primary purpose of the study - determining blood in the stool.

And if it is additionally possible to establish the type of pathogenic microorganisms that provoked intestinal inflammation, the diagnostic measure can even be considered overfulfilled. The disadvantage of immunochemical analysis is its duration: only after 2 weeks do doctors make a diagnosis.

Fecal occult blood tests are not prescribed for no reason. Typically, the patient complains of abdominal pain or malaise. General indications for the test are as follows:

• periodic or constant pain in the stomach;
• regular nausea, vomiting, diarrhea, or heartburn;
• chronic bowel disorder;
• rapid loss of body weight for no apparent reason;
• to confirm the diagnosis (for ulcers, gastritis, etc.).

Essentially, the purpose of the analysis is to detect damage to the walls of the intestines and stomach. And if the doctor insists on a detailed study of stool, the patient should not refuse.

The test is carried out without any internal interventions, so it will not hurt. However, the high sensitivity of the reagents requires special preparation of the patient.

Preparing for a stool occult blood test

Any research has an error. But in order for the results to be reliable, you must follow a diet before the analysis. First of all, you will have to give up meat and fish, because they contain hemoglobin.

The list of restrictions also includes iron-containing and all red foods (tomatoes, beets, etc.), which even color the stool healthy person. Diet is the key point, but doctors also name other requirements:

1. Discontinue medications 1 week before the test.
2. Ban on laxatives (including folk ones).
3. The day before the test, you should not brush your teeth (there is a risk of damaging your gums and distorting the results).
4. The analysis is carried out no earlier than 3 days after the x-ray examination.
5. Enemas are excluded (emptying should be natural).
6. Women get tested on days when they are not menstruating.

How to take feces correctly?

Not every person is able to observe such a prohibition as “you cannot eat.” Preparation for analysis requires mandatory implementation this point, otherwise the result of the study will be very doubtful. But the process of collecting feces itself is also important:

• It is necessary to prepare a container (sold at the pharmacy).
• Feces are needed without any liquid (water, urine, etc.). To do this, it is allowed to lay oilcloth in the toilet.
• After emptying, take 3 pieces of feces with a teaspoon.
• Samples should be delivered to the laboratory within 3 hours.

A small amount of blood still enters the intestines - 1-2 ml. This is normal only if this volume is the daily limit.

Therefore, the analysis will always show the presence of blood in the stool, but can such a small amount be considered a sign of a disorder? No. No one has canceled natural processes, and doctors only take into account larger indicators.

False results

To obtain reliable results from a fecal occult blood test, preparation should not be ignored. And if you treat this process carelessly, the results are often false.

Moreover, both false negative and false positive. For example, doctors know for sure that a patient has polyps in the large intestine, but the analysis does not detect hemoglobin.

This is due to the fact that such neoplasms do not bleed constantly, but only periodically. But it would be foolish to deny the presence of polyps, especially if detected using an endoscope.

False positive result- Same common occurrence. If the patient has neglected the rules for preparing and collecting stool, then it is quite possible that the study will show the presence of high level hemoglobin in the absence internal bleeding. The analysis is usually carried out using the Gregersen method, which is sensitive specifically to iron.

By eating only 1 apple the day before taking stool, a person will simply distort the results. In addition, blood can enter the intestines due to trauma to the gums with a toothbrush.

Thus, failure to comply with the rules will give doctors a reason to perform a colonoscopy, the essence of which is to insert a probe through the anus. It’s better to undergo such an unpleasant procedure not because of your own negligence!

What does a positive result mean?

Still, the analysis may show the presence of high levels of hemoglobin in the stool. In this case, a colonoscopy is prescribed to clarify the diagnosis, because there are many causes of bleeding:

• ulcer;
• inflammation in any departments;
• Crohn's disease;
• hemorrhoids;
• tuberculosis;
• intestinal fissure;
• good or malignant tumor(polyps, cancer, cyst, etc.).

Often blood enters the intestines from the mouth or nose. However, vascular damage in easily accessible areas of the body is easily determined by the appropriate doctors (dentist and otolaryngologist).

Conclusion

Fecal occult blood testing is an important diagnostic tool. Sometimes only hemoglobin impurities indicate pathological process in the intestines. And if violations are identified in a timely manner, then treatment will not be long in coming.