Feces for occult blood: purpose and preparation for analysis. Preparation for the analysis of occult blood in stool Analysis of stool for occult blood by the author

It is known that from a blood test we can determine whether a patient has chronic anemia. Its positive confirmation in the form of a low content of red blood cells - erythrocytes, a decrease in hemoglobin levels indicates the presence of blood loss. Moreover, bleeding can be sluggish, periodic and hidden. And when it is not possible to identify obvious sources of bleeding, a special stool test for blood was invented.

Taking a test, conducting a study, how to test feces for occult blood?

Indications for analysis

The analysis is needed to determine whether there is damage to the gastrointestinal tract. If the integrity of the mucous membrane of at least one organ is compromised, this will be visible in the results.

The reasons for the analysis may be:

Severe intestinal diseases.
Ulcer.
Colitis.
Polyps.
Anemia.
Poor appetite.
Abnormal stool.
A sharp change in weight downward.
Frequent constipation.
Heartburn.
Acute pain in the abdominal area.
Constant nausea.

In addition, feces for occult blood are taken if there is a suspicion of cancer or a benign neoplasm.

Let us remind you that you can get a referral for analysis from a surgeon, therapist, oncologist or gastroenterologist.

What do you need to know about the study?

At the present stage, everyone who undergoes an occult blood test needs to have at least general information on this matter.

The fresher the sample, the more accurate the results will be.
Before taking samples, simple preparation is required for several days.

The daily amount of dense excrement is approximately 200 grams. Significantly more comes out with pathological processes of the gastrointestinal tract, less with malnutrition, consumption of protein foods, and problems with bowel movements.

By the form you can understand whether there are deviations in the functioning of the intestines. In a healthy person, stool is sausage-shaped, medium-density, brown in color. If abnormal, excrement can be very dense or liquid, lumps or in the form of a ribbon. In severe pathologies, not only the appearance changes, but also the composition, smell, and various impurities appear.

Normal feces may contain particles of undigested food - the norm is the peel of fruits or vegetables, cartilage or tendons.

If mucus or blood is visible to the naked eye, this indicates a disease of the colon.

How to properly collect material and test feces for occult blood?

Almost all patients know how medical staff should behave. However, few people remember that there are also general recommendations for patients regarding taking any test, including stool. They are as follows.

Feces are collected after natural bowel movements. The use of enemas or laxatives is prohibited. It is not recommended to use it several hours before sample collection, and special preparations for another 3-4 days. If you break this rule, the analysis will not be accurate. However, this only applies when feces are tested for occult blood.

The accuracy of the results depends on the freshness of the material. The ideal option is if the sample reaches the laboratory within 3-6.5 hours after its collection. This rule is not always easy to follow, however, some microorganisms live outside for only a few hours. Therefore, it becomes increasingly difficult to obtain a complete picture over time. It is advisable to take the test before 10 o'clock.

3-4 days before submitting samples, special preparation is needed - following a diet. You should not eat a lot of foods that cause discomfort in the stomach and intestines. Avoid foods that stain excrement, such as beets, greens, and some fruits.

If possible, do not take pharmaceutical drugs a week before collecting samples. The exception is those taken regularly for chronic diseases. This is due to the fact that some medications color the stool a different color or change the composition of the microflora. In addition, do not conduct additional bowel examinations using special enemas, such as barium. It discolors feces and changes their structure.

Collect the sample in a special jar-container with a spoon, it must be purchased in advance. To make an accurate analysis, a few grams of material is enough. It looks like about a teaspoon.

The last rule applies to women. It is not recommended to take material during menstruation, as blood can get into the excrement and spoil the results.

Diet before stool occult blood test

A few days before the samples are taken, a special diet is prescribed, which must be followed in order for the analysis to be correct the first time.

During this period you should not eat, we repeat once again:

Liver in any form;
Legumes;
Fish and meat dishes;
Apples and other fruits that affect the color of feces;
Greens, particularly spinach;
Some vegetables: tomatoes, sweet peppers, beets, hot horseradish.

Sample menu for one day:

Bread and butter, milk soup, some pears or peaches, canned in winter;
Mashed potatoes, 2 boiled eggs, milk jelly;
Yogurt without dye;
A glass of kefir or fruit.

The amount of food taken at one time should not exceed 300-400 grams. The same set of foods with some corrections and variations should be eaten for another 2 days.

Feces for occult blood: interpretation of results

The finished analysis is called a coprogram. First of all, feces are not characterized by the presence of blood, even in the form of individual cells. Therefore, microscopic examination is done to find out whether red blood cells are present in the excrement?

They can be there for several reasons: damage to the stomach and small intestine or the lower part, that is, the rectum, colon and anus. If the bleeding is severe, the discharge is already noticeable - the feces will be black; in the case of minor damage, it is difficult to determine anything without special studies.

Damage to the lower part of the digestive system is noticeable due to the presence of bright red impurities. Since some foods and medications can have a similar effect, you need to undergo diagnostics, that is, donate feces.

This analysis will indicate whether there are problems at the top of the food system if red blood cells are present in the material provided for the study. There are no special standards for this; even the smallest amount of blood particles in the feces is enough.

If the gums or nasal mucosa bleed, the test will be positive. Therefore, careful preparation for the procedure is necessary, and it is not recommended to brush your teeth the day before and try to avoid various injuries.

Examination of feces for occult blood is one of the laboratory tests that makes it possible with a high degree of probability to diagnose internal bleeding in one of the sections of the gastrointestinal tract. Particular attention is required when preparing for a stool occult blood test, since if it is absent or performed incorrectly, false positive results may be obtained.

Indications for the purpose of analysis

Examination of stool for blood hidden in it is prescribed for the following patient complaints:

Constant/recurrent abdominal pain;
frequent symptoms of dyspeptic disorder - nausea, vomiting, heartburn;
regular diarrhea;
unexplained weight loss.

Testing stool for blood present in its composition is prescribed to confirm the diagnosis, for example, peptic ulcer or erosive gastritis. The overall goal of the analysis is to identify hidden damage to the mucous membranes of the stomach or intestinal tract.

Types of tests

If there are bleeding areas of the mucosa, blood may be present in a person's excrement. If the site of bleeding is the stomach or duodenum, then the stool becomes dark red in color. When the surface of the large intestine is damaged, they become scarlet. But it is not always possible to see blood impurities in a person’s stool. Very often, small ulcers bleed only periodically.

Laboratory testing of stool for occult blood can determine even the minimal amount of hemoglobin contained in it.

The study is performed in two ways:

Gregersen method (benzidine test);
immunochemical test.

The Gregersen test is quite informative, but only if the patient has thoroughly prepared

Gregersen's technique allows you to detect even the minimum concentration of hemoglobin. This is both an advantage and a disadvantage of the method. Benzodine colors iron molecules blue, but it reacts with both human and foreign hemoglobin (present in meat).

The immunochemical method is more accurate. Its significant drawback is that it takes quite a long time. Test results will be received only two weeks after submitting the material for research. Therefore, in most cases, stool testing is prescribed using the Gregersen method.

Preparing for the Gregersen test

To get the most reliable results, you need to properly prepare for stool donation. The recommendations will be as follows:

A week before the planned delivery, it is necessary to stop taking medications such as laxatives, bismuth- and iron-containing drugs, and non-steroidal anti-inflammatory drugs. It is prohibited to use acetylsalicylic acid and medications containing it.
It is necessary to avoid administering rectal suppositories.
Enema is prohibited.
Before testing stool for occult blood - two days before the test - you need to exclude any instrumental tests of the gastrointestinal tract. During the study, the mucous membrane may be accidentally damaged. Released blood may cause false positive results.
A few days before collecting excrement, you should stop brushing your teeth. Even a small amount of blood released when the gums are damaged can enter the stomach. And this hemoglobin can also negatively affect the final result.

Before the test is performed, the patient will be advised to follow a special diet. Its duration is 72 hours.

The main point of preparing for the test is strict adherence to the diet.

The patient's diet should completely exclude foods high in iron. The collection of stool must be preceded by refusal:

from apples;
cucumbers;
white beans;
spinach;
horseradish;
cauliflower;
meat and fish dishes;
offal;
green vegetables.

Ideally, in order not to make a mistake with the menu, doctors recommend adhering to a dairy diet during the days of preparation for donating stool. The diet may also include:

potato;
bread;
porridge (with the exception of buckwheat, oatmeal, egg, lentils, peas).

Collection of stool for research

Even careful preparation will be completely useless if the biological material is collected incorrectly.

There are special containers for transporting feces to the laboratory - they are sterile and guarantee the biological purity of the collected excrement

How to pass feces correctly? To obtain material suitable for research, you must follow the following recommendations:

A sterile container must be used to collect excrement. It can be purchased at any pharmacy. The set includes a jar with a lid and a special spoon.
First you need to empty your bladder. Then place an oilcloth in the toilet.
After bowel movements, it is necessary to take three portions of feces from different places.

The material must be delivered to the laboratory within the next three hours. It cannot be stored.

False results

Failure to follow the preparation rules before donating stool may result in erroneous results. They can be either false positive or false negative.

The main reason for false-positive tests indicating the presence of internal bleeding is improper preparation.

False positive results are quite common. The reason is a person’s disdainful attitude towards the preparatory stage. In this case, the test shows a high hemoglobin content in the absence of internal bleeding. Just one apple eaten a day before the delivery of biological material can distort the final results.

Proper preparation for examining stool for occult blood in many cases allows you to avoid a very unpleasant colonoscopy procedure. The technique involves examining the intestines by inserting equipment through the anus.

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 the digestive tract can be localized in both the upper and lower sections. If bleeding has opened in the stomach or duodenum, 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 is only a small admixture of hemoglobin in the stool.

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

Gregersen method (benzidine test).
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 for 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:

recurrent or constant abdominal pain;
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 foods and all red foods (tomatoes, beets, etc.), which color the stool of even a healthy person. Diet is the key point, but doctors also name other requirements:

Discontinue medications 1 week before the test.
Ban on laxatives (including folk ones).
The day before the test, you should not brush your teeth (there is a risk of damaging your gums and distorting the results).
The analysis is carried out no earlier than 3 days after the x-ray examination.
Enemas are excluded (emptying should be natural).
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 fulfillment of 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- also a common occurrence. If the patient neglected the rules for preparing and collecting stool, then it is quite possible that the study will show the presence of a high level of hemoglobin in the absence of 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, non-compliance 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;
benign 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 a pathological process in the intestines. And if violations are identified in a timely manner, then treatment will not be long in coming.

In order to determine the condition of the human body, you need to undergo an examination and submit some materials to a laboratory for research. There are a large number of types of tests, one of them is feces for occult blood. Preparation takes several days.

Collection of stool for occult blood: indications

The reasons for the analysis may be:

Severe intestinal diseases;
Ulcer;
Colitis;
Polyps;
Anemia;
Poor appetite;
Abnormal stool;
A sharp change in weight downwards;
Frequent constipation;
Heartburn;
Acute pain in the abdominal area;
Constant nausea.

In addition, feces for occult blood are taken if there is a suspicion of cancer or a benign neoplasm.

You can get a referral for analysis from a surgeon, therapist, oncologist or gastroenterologist.

What do you need to know about the study?

At the present stage, everyone who undergoes an occult blood test needs to have at least general information on this matter.

The fresher the sample, the more accurate the results will be.

Before taking samples, simple preparation is required for several days.

Normal feces may contain particles of undigested food - the norm is the peel of fruits or vegetables, cartilage or tendons.

If mucus or blood is visible to the naked eye, this indicates a disease of the colon.

Feces are collected after natural bowel movements. The use of enemas or laxatives is prohibited. It is not recommended to use it several hours before sample collection, and special preparations for another 3-4 days. If you break this rule, the analysis will not be accurate. However, this only applies when feces are tested for occult blood.

Collect the sample in a special jar-container with a spoon; it must be purchased in advance. To make an accurate analysis, a few grams of material is enough.

The last rule applies to women. It is not recommended to take material during menstruation, as blood can get into the excrement and spoil the results.

Diet before stool occult blood test

A few days before the samples are taken, a special diet is prescribed, which must be followed in order for the analysis to be correct the first time.

During this period you should not eat:

Liver in any form;
Legumes;
Fish and meat dishes;
Apples and other fruits that affect the color of feces;
Greens, particularly spinach;
Some vegetables: tomatoes, sweet peppers, beets, hot horseradish.

Sample menu for one day:

Bread and butter, milk soup, some pears or peaches, canned in winter;
Mashed potatoes, 2 boiled eggs, milk jelly;
Yogurt without dye;
A glass of kefir or fruit.

The amount of food taken at one time should not exceed 300-400 grams. The same set of foods with some corrections and variations should be eaten for another 2 days.

Feces for occult blood: interpretation

The finished analysis, interpretation, is called a coprogram. First of all, feces are not characterized by the presence of blood, even in the form of individual cells. Therefore, microscopic examination is done to find out whether red blood cells are present in the excrement?