How to get tested for occult blood. Why is an occult blood test needed?

People suffering from diseases of the stomach and intestines regularly take a stool test for occult blood. This test is used to detect asymptomatic bleeding from different parts of the digestive tract.

The study is carried out in a clinical laboratory, is not considered time-consuming. It is important in the differential diagnosis of anemia. Doctors are well aware of the rules according to which stool collection for occult blood should be organized in order to obtain reliable results. Patients should certainly familiarize themselves with them when they are sent to the laboratory.

Diagnostic methods are constantly being improved. In addition to the practice of the benzidine test (Gregersen reaction), tested over the years, immunochemical analysis appeared and became available. Detection of occult blood in the feces provides essential assistance to doctors in diagnosing the disease and choosing a treatment.

What blood is considered hidden?

First of all, you should define the terminology. If blood is visible on the surface of the stool after a bowel movement, then it does not apply to occult bleeding. It is already visible without any analysis. The cause of this symptom in adults is most often the rupture of hemorrhoidal veins, fissures in the rectum.

The test for occult blood in the stool means the detection of a sign that is imperceptible by the nature of the feces, when the presence of blood is not visible not only to the eye, but is also not determined by microscopic examination.

Laboratory techniques are able to show the presence of gastrointestinal bleeding with a blood loss of less than 50 ml. This is typical for the acute stages of the following diseases:

• peptic ulcer;
• intestinal polyps;
• tumors;
• nonspecific ulcerative colitis;
• erosive gastroduodenitis;
• diverticula of the stomach and intestines.

A malignant neoplasm is one of the causes of the appearance of occult blood in the feces.

In the differential diagnosis, the doctor should take into account the possible positive result:

• with bleeding from the nose, gums;
• inflammatory diseases of the palatine tonsils and pharynx,
• varicose veins of the esophagus caused by cirrhosis of the liver;
• esophageal ulcers and erosive esophagitis;
• Crohn's disease;
• tuberculous lesions of the intestine;
• helminths in a child;
• blood diseases.

Evaluation of the results of a fecal occult blood test is carried out by a doctor in combination with other studies and clinical manifestations. Detection methods have their own characteristics. In diagnostics, their intended purpose must be taken into account.

Examination of feces using a benzidine test

The benzidine test got its name from the main reagent in the reaction with feces for occult blood. It is more often used in the modification of Gregersen (Gregersen's test), which added barium peroxide and acetic acid to benzidine (paradiaminodiphenyl in chemical structure) for greater activation of the test solution.

The essence of the reaction: the use of the property of erythrocyte hemoglobin to oxidize benzidine. This method can detect microimpurities of blood (erythrocyte hemoglobin) not only in feces, but also in vomit, gastric juice. It is used for the examination of blood-like stains in forensic medicine. The sensitivity of the sample is 1:100,000. Remember the experiments of Sherlock Holmes (it is worth recalling that Conan Doyle was a doctor).

An important point: a positive result is obtained not only when exposed to hemoglobin, but also when the myoglobin of muscle tissue (in meat), some vitamins and drugs with benzidine react. This requires compliance with the preparatory period, dietary restrictions.

Benzidine test technique

The collected feces in a small amount are smeared on a glass slide. A few drops of the reagent are applied to it. If blood is present, a blue-green color is obtained.

With loose stools, the reaction is carried out on filter paper, through which excess liquid is absorbed

Who is assigned the Gregersen reaction?

The main area of ​​application is the diagnosis of bleeding from the stomach and intestines:

• when clarifying the nature and cause of anemia;
• hemorrhagic diathesis;
• suspicion of a cancerous tumor and intestinal polyposis;
• detection of activity of gastric and duodenal ulcers;
• suspected ulcerative colitis.

The simplicity of the study makes it possible to use it for preventive examinations of persons aged 50 years and older every two years. It helps in the early diagnosis of cancer.

What preparation is needed?

The possibility of a cross-reaction with myoglobin requires preliminary preparation of the patient 3 days before taking feces:

• it is necessary to exclude from the diet meat and fish products, dishes from the liver;
• at the same time, you can not eat iron-rich vegetables and fruits (apples, spinach, bell peppers, white beans, green onions, zucchini, tomatoes, cauliflower);
• you should stop taking iron supplements, vitamin C, Aspirin and headache remedies containing it, non-steroidal anti-inflammatory drugs (Diclofenac, Naprofen, Ibuprofen);
• laxatives and enemas are contraindicated;
• to eliminate the influence of bleeding gums, it is not recommended to brush your teeth.

If shortly before being sent for research, diagnostic methods such as sigmoidoscopy, colonoscopy, x-rays of the stomach and intestines were used, then taking feces for occult blood should be postponed for three days. Girls and women should not take a stool test for occult blood during menstruation. Lack of preparation leads to false positive results.

In infants, material for research is taken from a diaper

Evaluation of the results of the benzidine test

Deciphering the analysis of feces for occult blood and interpreting the results is up to the doctor. The reaction is evaluated only qualitatively, a negative result is noted in the conclusion of the laboratory.

How intense the outcome of the test can be judged by the number of crosses: from one (+) to four (++++). Sometimes instead of (+) they write "traces". In any case, this means the possibility of asymptomatic bleeding, if the rules for preparing and collecting feces for occult blood are not violated.

How to collect feces for analysis?

Feces for occult blood testing should be taken naturally on the day of the test, without enemas or laxatives. People with constipation will have to wait for a chair, having a direction on their hands.
The pharmacy sells special sterile containers with a spoon and a tight lid.

In children, feces are collected from a pot, in infants - from a diaper. It would also be right for an adult to adapt the act of defecation into a clean pot or vessel, onto cellophane or a piece of paper.

Special rinsing before collection is not required, normal hygiene procedures with warm water are suitable.

The container must be delivered to the laboratory by 10 am

For research, the amount of feces with a volume of a teaspoon is sufficient. You need to take the biomaterial little by little from 2-3 different sites. The material for the study should be collected on the same day on which the analysis is scheduled. It is better not to delay transportation. Short-term storage in the refrigerator at a temperature not lower than +6 degrees is allowed.

Immunochemical method and its advantages

The study of feces for occult blood by the immunochemical method has several advantages over the Gregersen reaction:

• sensitivity is much higher;
• specific only to human hemoglobin, does not respond to meat myoglobin, vitamins and drugs;
• does not require special dietary preparation;
• more suitable for diagnosing bleeding from the lower intestines, because the technique uses a reaction to the protein part of hemoglobin, and it is actively digested in the upper gastrointestinal tract.

The test is included in the algorithm for examining patients with suspected colorectal cancer (with localization in the colon and rectum). The result of the analysis does not contain information about the specific area of ​​the bleeding digestive system and the causes of bleeding.

It should not be treated as a ready-made diagnosis. In the case of a positive result, the test shows that an additional colonoscopy is recommended to identify the cause of the bleeding. The essence of the method: the use of antibodies to human hemoglobin allows you to identify the presence of antigens in the test material and give a quantitative characteristic.

When is an immunochemical study indicated?

The main indications for the study of the pathology of the lower intestines is the suspicion of:

• on the tumor
• polyps;
• ulcerative colitis;
• Crohn's disease.

The use of the technique in the early diagnosis of colorectal cancer (the most common cause of oncological mortality in the population) helps to conduct a follow-up examination in a timely manner and improve the prognosis of the course of the disease.

The population screening algorithm provides for a priority immunochemical study with the delivery of feces by all persons over 50 years of age, and in case of hereditary problems from the age of 40 - three times. If a positive result is detected, a colonoscopy is prescribed.

Experts believe that following this program can reduce the death rate from colorectal cancer by 25%.

Immunochemical study technique

The technique uses the principle of immunochromatography:

• a drop of the test material is placed in the well of the tablet, in which a reagent with specific antibodies and a dye has been previously applied;
• in the presence of an antigen from the hemoglobin of erythrocytes, a reaction occurs between them;
• a colored complex is formed;
• with the liquid, the complex passes into the test zone, along the way it additionally connects with antibodies;
• in the testing area, a certain threshold level of hemoglobin concentration is set, its excess in the sample is manifested by pink-purple markings.

The laboratory assistant can conduct several analyzes at once

How are the results interpreted?

The test gives a false-negative answer if there is no free hemoglobin in the stool sample, there are only undestroyed red blood cells, for example, if there is external bleeding from an anal fissure.

The physiological loss of RBCs in the feces forms the limit for the normal result level of -14 ng/mL. Diagnostic thresholds are set depending on the objectives of the study. For example, to detect cancer at risk - 50 ng / ml is considered a normal concentration of free hemoglobin.

Is special preparation required for analysis?

Unlike the benzidine test, no special dietary restrictions are required. But there are some peculiarities:

• it is necessary to resolve with the attending physician the question of the possibility of using drugs that increase the risk of bleeding (Aspirin derivatives, non-steroidal anti-inflammatory drugs) before the study;
• the analysis is not carried out within 14 days after instrumental studies of the stomach and intestines, cleansing enemas, colonoscopy, sigmoidoscopy (they can cause damage to the mucous membrane);
• it is not recommended to take feces from the toilet; it is better to use a sheet of paper, oilcloth, cellophane;
• the standard container must be filled 1/3;
• delivery to the laboratory must be ensured within 12 hours after defecation;
• it is possible to store the sample in a refrigerator at a temperature of plus 4–8 degrees until transportation.

Feces must be obtained without enemas and laxatives

Is accelerated express diagnostics possible?

The question of how long the analysis is done needs to be found out in the laboratory where the research material is delivered. In the pharmacy network you can find a specific test "ImmunoCHROME-GEM-Express". This is a variant of the immunochemical rapid determination of hemoglobin.

You can do it at home. But first, you should carefully read the instructions and follow the preparation requirements. It takes several minutes to get the result of the benzidine test. The patient can receive the conclusion by the end of the working day. An immunochemical test will require 3-6 days.

Conducting a study of feces for occult blood is an important point in the diagnosis of many diseases. The preparation and rules for passing the analysis should be taken seriously. This will avoid serious complications in the future.

In order for the analysis of feces for occult blood to show reliable results, appropriate preparation is necessary. Diagnosis and treatment depends on laboratory tests. Be sure to follow all the recommendations of your doctor regarding the diet before collecting the material.

Why you need to take an analysis

Already from the name of the laboratory study it is clear what the analysis of feces for occult blood shows. Then the question arises: to whom and for what purposes is he appointed? This analysis allows you to identify the presence of bleeding in the gastrointestinal tract, which, in turn, can occur for a variety of reasons. For example, for these:

• intestinal inflammation;
• ulcerative colitis;
• stomach ulcer and / or duodenal ulcer;
• diffuse familial polyposis;
• polyps in the large intestine;
• cirrhosis of the liver;
• hemorrhoids and anal fissure;
• helminth damage.

If there is a history of one of these pathologies, or its symptoms, fecal occult blood tests are indicated.

Preparation and delivery of analysis for adults

This analysis may be relevant for diagnosing various diseases of the gastrointestinal tract in both adults and children. See the link for the breakdown.

Having ordered a fecal occult blood test, the doctor must tell you that special preparation is required before this laboratory test.

6 mandatory stages of preparation

1. A week before the delivery of feces, stop taking medications, and especially those that can affect the motility of the gastrointestinal tract and the color of the material. This rule applies to all forms of preparations, including oral (tablets, capsules, potions, infusions) and rectal (oils and suppositories).
2. Before passing the analysis, strict adherence to the diet will be required. Exclusion from your diet of certain products (which ones - read below) at least 72 hours before the day of sampling.
3. Defecation to collect material should be only spontaneous. No enemas or laxatives.
4. If any diagnostic examinations in the area of ​​the intestine or stomach, for example, sigmoidoscopy or endoscopy, were prescribed, they must be rescheduled for another time (after fecal sampling for analysis).
5. Although this rule contradicts hygiene standards, it is recommended not to brush your teeth the night before giving feces, but simply rinse your mouth. The fact is that even the most microscopic trauma to the gums can affect the result of the study.
6. During menstruation, women cannot donate feces for occult blood for analysis. We'll have to reschedule the study for another day.

Kirimov P.A., proctologist, clinic “Health plus”, Moscow

After the age of 40, the risk of cancer is known to increase.

Therefore, even if there are no health complaints, it is imperative to come to the local therapist for a referral for analysis, or be examined in a private clinic.

Diet before testing

What should be the diet of the examined patient should be indicated separately. A special diet before analyzing feces for occult blood must be observed for at least 3 days.

Gregersen's method, according to which this analysis is carried out, is sensitive to iron, therefore, it is highly recommended to exclude all products containing this element.

Also, from the menu, you should remove food that can change the color of feces (blueberries, beets), promote constipation (rice, pastries from premium flour) or have a laxative effect (prunes, strawberries), causing flatulence (beans, soda).

So, you will need to exclude from your diet everything that can make the results of a fecal occult blood test false:

• fish and some seafood;
• meat and offal;
• most vegetables (especially those that contain a lot of iron or have a laxative effect);
• fresh apples;
• berries, especially blueberries, strawberries and black currants.

What can you eat in this case? Include grain bread, butter, various cereals, chicken or quail eggs, dairy products in your diet. In small quantities, it is allowed to eat baked or boiled potatoes and some fruits.

1. The container for transporting feces must be sterile. As a rule, this is a plastic or glass container with a tight-fitting lid. When using non-standard containers, it is necessary to boil it. described in detail in our article at the link.
2. After defecation, the material must be collected from 3-4 places of a single portion. A volume equal to half a teaspoon will be enough. Contact with feces of secretions from the urinary tract is unacceptable.
3. The sooner the material is delivered to the laboratory for analysis, the better. You can store it in a special container for a maximum of 12 hours, while the temperature should be from +4 to +8. If these conditions are not met, the result will be false.

How to prepare and pass the analysis to the child

Parents are responsible not only for their own health, but also for the health of their children. You need to be attentive to the well-being and mood of the child, do not ignore complaints of pain. Toddlers who can't speak express their anxiety with strong incessant crying. and if at the same time there is a delay in stool or diarrhea, it is urgent to take a stool test, including occult blood.

Training

All recommendations for preparation for analysis, including a special diet and drug withdrawal, are followed in children in the same way as in adults. Soda and various sweets with dyes are harmful to the gastrointestinal tract, and if you have not yet limited your child from their use, you definitely need to do this when preparing to donate feces.

Children in the first months of life usually eat only mother's milk. Therefore, in order for the analysis of feces for occult blood in infants to be reliable, a nursing mother must follow an appropriate diet and exclude medications for a while. and read the articles at the link.

Polyakova V. I., pediatrician, children's polyclinic No. 1, Voronezh

Not always pathologies of the gastrointestinal tract are manifested by painful sensations, frequent defecation or its delay.

After each bowel movement, carefully examine the contents of the potty or diaper.

Collection, storage and transportation of material

General recommendations have already been described above on how to collect a fecal occult blood test. Urine in the container is unacceptable. It is not advisable to wear a diaper for the collection and delivery of material to the baby, as this can spoil the picture of the results. It is best to use a clean fabric oilcloth.

As for older children, then take feces after a bowel movement from the toilet is unacceptable. Ask the child to recover in a pot, which should first be doused with boiling water.

It is also necessary to store children's feces at a temperature of +4 to +8 and transport it to the laboratory no later than 12 hours.

Deciphering the results: norm and deviation, false positives and false negatives

Deciphering the analysis of feces for occult blood, like any other laboratory study, is always performed by the attending physician. You should not draw any conclusions on your own, and even more so self-medicate.

Norms and deviations in adults

The norm of the analysis of feces for occult blood is a negative result. But at the same time, it should be understood that 1-2 ml of blood still enters the intestines. This will also be considered a variant of the norm, but only if the chair is not more than 1 time per day.

If the fecal occult blood test is negative, but other studies indicate the presence of pathologies of the gastrointestinal tract (for example, polyps in the rectum are clearly detected during endoscopy), the result is considered false negative.

A positive result in most cases indicates the presence of pathologies of the gastrointestinal tract, liver. These can be polyps, ulcers, fissures, hemorrhoids and even a malignant tumor. Other methods of research will be required to clarify the diagnosis.

If the fecal occult blood test is positive, you should not immediately panic. Before making a diagnosis, the doctor will prescribe a second examination. After all, it is quite possible that the results are false. Distortions can occur for the following reasons:

• non-compliance with a special diet and other recommendations before the study;
• bleeding in any part of the gastrointestinal tract is still present, but is temporary;
• bleeding gums, nasal mucosa (you should definitely inform your doctor about this).

In addition, errors on the part of the laboratory are not ruled out. Such cases are rare, but they do happen.

Norms and deviations in children

In children's feces, as in adults, there should be no blood(more about). But at the same time, it should be understood that during the first 3 months of life, the baby's body adapts to extrauterine life, and the gastrointestinal tract is still continuing to form. Therefore, if in a small child the analysis showed occult blood in the feces, minor deviations from the norm are allowed.

The fact is that in an unformed intestine, the vessels are located very close to the surface and are easily deformed during defecation, and even with strong gas formation.

In this case, as well as with bleeding gums during teething, and with improper preparation for analysis, a false positive result is possible.

But the situation cannot be left to chance either. First of all, you need to try to bring the baby's stool back to normal by reviewing. In case of gas formation, lay the child on the tummy more often and give dill water. After these actions, it is imperative to retake the fecal analysis, and if necessary, the pediatrician will prescribe a hardware examination.

It is necessary to examine the stool in older children, even in the absence of complaints, at least once every six months for preventive purposes.

The presence of occult blood in the feces of a child can often indicate damage to the liver and gastrointestinal tract by helminths.. This disease in childhood is quite common, however, there are no obvious symptoms. Therefore, it is important to know.

In pediatrics, medical prescriptions should be treated with particular caution. Unpromising and aggressive treatment can harm the health of the child. It is necessary to strictly monitor all indicators, for example, to know what is the norm of blood sugar in children.

Conclusion

Unfortunately, there are very few completely healthy people in the modern world. This situation is aggravated by the fact that many pathologies are latent and are already detected at an advanced stage.

In order to detect the disease in time, regular diagnostics are necessary.: hardware and laboratory research. If the analysis is normal, and complaints persist, you should repeat the studies, as well as undergo additional diagnostics, for example, ultrasound, endoscopy, sigmoidoscopy, FGDS. Remember, our health is in our hands.

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:

Fecal occult blood analysis is a fairly commonly prescribed diagnostic method. Currently, it is recommended to a large number of patients, both therapeutic and surgical.

Why is it needed?

Analysis of feces for occult blood: how to donate?

Many do not know how to prepare for this procedure. As a result, there are quite a lot of false positive results of such a study. That is why it is important to know how to properly take a fecal occult blood test. Preparation of the patient in the form of a diet is carried out within 2, and preferably 3, days. In the future, after the act of defecation, it is necessary to take a small clean stick and separate a small sample from the feces (preferably 2 samples from different areas) and put it in a previously prepared container or box. After that, it is necessary to take the feces to the laboratory for research.

Some healthcare facilities provide their patients with special stool collection kits. There are several varieties of them at once. Most often, we are talking about a small clean stick and a folding paper box with several "windows" for applying a stool sample to them. More modern containers for the analysis of feces for occult blood are jars that close with a lid with a small stick facing the inside of the container. At the same time, there is a special liquid inside, which allows you to effectively conduct research.

Where can I get a referral for testing?

To date, a referral for such a study can be obtained in a fairly large number of medical centers. At the same time, both therapists and surgeons can provide it. The cost of such an analysis can vary significantly depending on which center the patient applied to: public or private. As for the former, they can provide a referral for a fecal occult blood test and can even send it for free.

What to do after analysis?

If the stool test is positive, the patient is referred for a colonoscopy. After it is carried out, in the presence of serious morphological changes that make the doctor suspect oncological diseases, the person is sent for additional examination in order to clarify the presence of similar pathological processes in other organs and tissues. In addition, the patient is referred for computed or magnetic resonance imaging. This helps to determine the size and extent of the tumor. In the future, such a patient should be obligatorily observed by an oncologist.

The most common causes of blood in the stool

In addition to various kinds of oncological processes of the gastrointestinal tract, a similar symptom is also characteristic of other diseases. First of all, it should be noted hemorrhoids and anal fissure. With these pathologies, an admixture of scarlet blood is found in the feces. Most often, it is located on the stool sample itself, and not mixed with it. Polyps and diverticula can also bleed. In the case of these diseases, the blood is darker and may be mixed with feces.

Black (tarry) feces occurs when a person has a gastric ulcer with bleeding. This pathology is very dangerous and requires immediate hospitalization. Moreover, it is quite possible that such a disease will have to be treated with the help of surgical intervention. Bleeding from esophageal varices can also lead to a positive fecal occult blood test.

What can you do yourself?

In the event that a person finds that a certain amount of blood has been excreted in his feces, he needs to consult a doctor. Moreover, if this symptom is accompanied by other clinical manifestations, then you should visit a doctor as soon as possible. Naturally, you should not use any medicines on your own, since in some cases they can only do harm. Moreover, you do not need to try to help yourself on your own with the help of various folk recipes. In this case, they can be even more dangerous than drugs.

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

The essence of the analysis

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

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

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

When an examination is ordered

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

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

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

Types of occult blood tests

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

Benzidine test

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

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

Immunochemical analysis

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

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

Preparation for analysis

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

How to properly collect feces?

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

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

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

Deciphering analyzes

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

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

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

What does a positive result mean?

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

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

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

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

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