Diet before donating feces for occult blood - a few secrets in order to do everything correctly. Taking a stool occult blood test: preparing for the test

Fecal occult blood testing 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?

Fecal occult blood test: how to take it?

Many people do not know how to prepare for this procedure. As a result, there are quite a lot of false positive results from such a study. That is why it is important to know how to properly take a stool test for occult blood. The patient is prepared in the form of a diet for 2, or preferably 3, days. Subsequently, after defecation, you need 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 this, you need to take the stool to the laboratory for testing.

Some medical institutions provide their patients with special stool collection kits. There are several varieties of them. Most often this involves a small clean stick and a folding paper box with several “windows” for applying a stool sample. More modern containers for testing feces for occult blood are jars that are closed with a lid with a small stick facing the inside of the container. At the same time, there is a special liquid inside that allows you to effectively conduct research.

Where can I get a referral for tests?

Today, a referral for such a study can be obtained in a fairly large number of medical centers. Moreover, it can be provided by both therapists and surgeons. The cost of such an analysis can vary significantly depending on which center the patient goes to: public or private. As for the former, they can provide a referral for a stool test for occult blood and can even send it for free.

What to do after the analysis?

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

The most common causes of blood in the stool

In addition to various types of oncological processes of the gastrointestinal tract, a similar symptom is characteristic of other diseases. First of all, hemorrhoids and anal fissure should be noted. With these pathologies, an admixture of scarlet blood is detected in the stool. Most often it is located on the stool sample itself, rather than mixed with it. Polyps and diverticula can also bleed. In these diseases, the blood is darker and may be mixed with the stool.

Black (tarry) feces occur 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 surgical intervention. Bleeding from esophageal varices may also result in a positive stool occult blood test.

What can you do yourself?

If a person discovers that he has released a certain amount of blood in his stool, 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 medications on your own, since in some cases they can only cause harm. Moreover, there is no need to try to help yourself on your own with the help of various kinds of folk recipes. In this case, they may turn out to be even more dangerous than medications.

Indications for taking an occult blood test are:

· stomach ache;

· heartburn;

· nausea;

· constipation;

· weight loss;

· pasty stools;

· decreased appetite;

· anemia;

· stomach ulcer;

· nonspecific ulcerative colitis;

· polyposis;

· intestinal tuberculosis.

The patient is prescribed a three-day diet before the occult blood test. She excludes fish and meat, liver, green vegetables, white beans, spinach, pomegranates, apples, bell peppers, beets, horseradish, tomatoes and blueberries from her diet. At the same time, the diet before an occult blood test includes potatoes, cereals, dairy products, boiled eggs, butter, bread, and a small amount of fresh fruit.

Before testing feces for occult blood, the diet excludes not only the consumption of certain foods, but also the use of medications containing iron. These drugs include: bismuth and barium sulfate. They can affect the color of stool.

Also, before testing feces for occult blood, the diet, in addition to limiting certain foods, prohibits the use of laxatives, rectal suppositories and drugs that affect intestinal motility.

Two days before the test, it is not advisable to brush your teeth with a toothbrush, as this can damage the gums and blood from the mouth will enter the stomach.

Women are not tested for occult blood during menstruation.

You should not give an enema on the eve of the test, as it can damage the mucous membrane and lead to incorrect results.

Mixing urine with feces is unacceptable.

Following a diet before an occult blood test and following all the recommendations described above can guarantee accurate test results.

Procedure for taking a stool occult blood test

The collection of material for analysis occurs in the same way as for a general analysis of stool. A glass or plastic container or a special container is used as a container.

Stool collection is carried out from four places of fresh feces, excluding urine from entering them. To obtain the most accurate results, it is necessary to deliver stool to the laboratory within three hours after defecation.

More precise recommendations that are important for the diagnosis of a specific disease can be given by the attending physician. A similar analysis can be taken at a medical institution at your place of residence. In addition, you can take a stool test for occult blood in numerous medical centers and private laboratories at any convenient time. Test results will be ready within six days. The normal result of a stool occult blood test is negative.

Can the test result be false?

It happens that the analysis gives a false result. Most often, when the occult blood diet is not followed, or there is bleeding localized in the gums, a false positive test result is observed. Thus, strict adherence to the occult blood diet is a prerequisite before taking the test.

False negative test results are also possible. This happens in cases where the bleeding is not constant, but is periodically renewed.

In general, the sample is quite reliable, but to confirm the results, tests must be taken twice. If all the conditions are met before donating stool for occult blood, the diet is followed, samples are taken at intervals of 3-4 days, and the test result turns out to be the same, then it is reliable.

Positive test result

When the occult blood diet is followed, all the conditions for preparing for the test are met, and the test result is positive, this may indicate an ulcerative, oncological or inflammatory process. A positive test is a serious reason for diagnosis. If the doctor has written a referral for an occult blood test, the diet before taking it must be strictly followed.

For timely diagnosis and to avoid aggravation of the disease, the test must be completed at the first request in compliance with the required preparation. The sooner a correct diagnosis is made, the sooner it is possible to prescribe effective treatment.

Quantitative immunochemical test

Today, there is a relatively new method for determining occult blood - this is a quantitative immunochemical test. It is used in the diagnosis of colorectal cancer. Preparation for the test is minimal. To determine occult blood, you simply need to take a stool test, and there is no need to follow a diet.

A diet is not needed for the reason that this study uses antibodies to hemoglobin. Such antibodies do not react to myoglobin contained in eaten animal meat. The test is specific, characterized by high sensitivity and accuracy. The absence of the need to follow a diet makes this method very convenient for patients.

An occult blood test makes it possible to diagnose a number of diseases even before they cause irreparable harm to the body.

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:

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 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:

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 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.

A blood test may indicate chronic anemia if the patient has intermittent bleeding.

If there are no obvious bleedings, doctors continue diagnostics until detection causes of anemia.

A routine blood test cannot determine the source of the bleeding. Therefore, to determine the cause, additional tests are carried out, including a stool occult blood test, which allows you to find blood in the gastrointestinal tract.

A fecal occult blood test is a test designed to for diagnosing minor bleeding from any part of the digestive tract. The test owes its name to the fact that small amounts of blood in the stool are quite difficult to detect. A small amount of blood does not change the consistency of stool or its color. This means that bleeding can only be detected using special tests.

The occult blood test helps detect hemoglobin in red blood cells when this cannot be done either by microscopic examination or visually.

During a laboratory test, hemoglobin is looked for in a stool sample. To do this, a reagent is added to the feces, which, interacting with hemoglobin, promotes the appearance of a chemical reaction. This technique allows us to identify the presence of even slight bleeding in the gastrointestinal tract.

The disadvantage is the following: the test allows you to detect even an insignificant amount of hemoglobin, which does not always indicate the presence of bleeding.

In other words, analysis can even reveal that hemoglobin, which had entered the human stomach the day before during a meal. To avoid such a mistake, you need to properly prepare for the test.

A positive test indicates the presence of an ulcer, oncology or inflammation, so even an insignificant amount of blood in the digestive organs is a cause for concern. It must be remembered: in some cases, the analysis may incorrectly reflect the picture of what is happening.

The reason for the false result may lie in improper preparation for testing and in other bleeding - from the nose and gums. In order to verify the correctness of the result obtained, stool analysis must be done twice, with an interval of several days. In the event that a test produces the same “verdict” twice, it can definitely be trusted.

Preparation

Any physician who has doubts regarding the patient’s health can prescribe an occult blood test: a general practitioner, gastroenterologist, oncologist or surgeon. In this case, the doctor must warn the patient that it is necessary to properly prepare for the test. This preparation includes following certain recommendations.

• 7-10 before analysis stop taking the following medications: laxatives, anti-inflammatory, bismuth- and iron-containing, non-steroidal. Also during this time, it is prohibited to take acetylsalicylic acid and drugs that contain it (Aspirin).
• Stop administering rectal suppositories and oils.
• Don't give enemas.
• Do not conduct any diagnostic tests in the gastrointestinal tract for 1-2 days before submitting stool samples. Failure to comply with this requirement can injure the mucous membrane and, as a result, obtain an unreliable result.
• Observe special diet within 72 hours before donating stool.
• Give up the habit of brushing your teeth for a while. The slightest amount of blood that appears when the gums are damaged is highly likely to end up in the gastrointestinal tract.

What can you eat?

To get a reliable result, you need to “go on a diet” 72 hours before the test. This diet does not prohibit the consumption of dairy products, potatoes, some cereals and bread. The main thing is to avoid eating foods high in iron.

If you are unsure about which foods you can and cannot eat before getting tested, talk to your doctor about this topic.

Prohibited Products

Three days before taking a stool sample for occult blood eliminate the following foods from your diet:

• some fruit and vegetable crops, namely: apples, white beans, cucumbers, spinach, cauliflower, horseradish);
• meat and chicken dishes, offal, fish dishes;
• green vegetables, tomatoes;
• iron-containing products, for example, bell pepper.

Failure to comply with this requirement may result in tiny particles of hemoglobin getting into the stool, the results obtained will be unreliable, and the test will have to be done again. To avoid such a development of events, carefully prepare for the analysis and do not neglect the recommendations of your doctor.

Usually, the appointment of a stool occult blood test has a serious basis. If your doctor has given you a referral for this test, you need to take it as soon as possible. If you receive a positive result, you should not panic.

Remember: the sooner the disease is detected, the sooner treatment will be prescribed that can eliminate this pathology and restore your lost health.

Pathologies of the duodenum, stomach, and esophagus may be accompanied by internal bleeding. Stool analysis helps identify them at an early stage. The study detects occult blood, which often becomes a sign of cancer.

What is occult blood in stool

Traces of blood in excrement that are invisible to the human eye are called occult blood. They are detected only when special tests are carried out to detect transferrin or hemoglobin. The study gives the most reliable results in identifying the following pathological conditions:

• ulcer of the duodenum, stomach;
• helminths in a child;
• tuberculosis of the intestine;
• blood diseases;
• varicose veins of the esophagus;
• Crohn's disease;
• erosive esophagitis;
• cirrhosis of the liver;
• Lynch syndrome;
• hemorrhagic diathesis;
• tumors;
• polyposis;
• inflammation of the tonsils, pharynx.

Stool analysis can detect colorectal cancer and intestinal tumors at an early stage. Positive test results are typical for the following pathologies:

• diverticula of the intestine, stomach;
• erosive gastroduodenitis;
• nonspecific ulcerative colitis;
• damage to the mucous membrane of the digestive organs.

When is an occult blood test prescribed?

Doctors prescribe a stool test for patients when signs of digestive system diseases appear. Indications for research are the following symptoms:

• abdominal pain of unknown etiology;
• false urge to defecate;
• causeless loss of body weight;
• diarrhea;
• constipation;
• hyperthermia;
• nausea;
• heartburn;
• vomit.

Methods for detecting occult blood in stool

If internal bleeding is suspected, doctors use different methods of examining stool. They are distinguished by sensitivity, efficiency, the need for preparation, and the identification of pathologies in various parts of the intestine. Diagnostic methods for occult blood, their advantages and disadvantages:

Benzidine test	instant results; high sensitivity; availability; low price	required: careful preparation; following a strict diet; correct collection of biomaterial
Immunochemical test	no dietary restrictions required; high accuracy, sensitivity; efficiency; lack of reaction to hemoglobin in foods, medications	not carried out everywhere; high price; objectivity only in case of blood loss in the lower intestines (enzymes of the small intestine and stomach interfere with the reaction)
Guaiac test	availability; efficiency	sensitivity only to large blood losses; high demands on diet; the test is performed 6 times

Benzidine test

This stool test to detect hidden blood loss has a second name - Gregersen's test. The main reagent is benzidine, to which acetic acid and barium peroxide are added to increase activity. The technique gives many false positive results - a reaction to nosebleeds, eating meat, drugs, bleeding gums.

Immunochemical test

Surgical research detects tumors in the colon at an early stage and reduces cancer mortality by 30%. Immunochemical analysis of feces for occult blood reacts only to human protein and does not require special preparation. It is characterized by high sensitivity and the following features:

Guaiac test

The sensitivity of the guaiac test depends on the hemoglobin concentration. If its content is more than 2 mg per gram of feces, the result is positive in 90% of cases. The test diagnoses bleeding in any part of the digestive system. The analysis has the following specifics:

Rules for preparing for research

To obtain an accurate test result, proper preparation is important. The process begins a week before the analysis and includes the following activities:

Time to study	What to do
	eliminate laxatives; don't use enemas	affect intestinal motility
	stop taking: preparations containing iron; non-steroidal anti-inflammatory drugs; Aspirin; vitamin C	change the color of stool
	don't have anal sex	possible damage to mucous membranes
	remove from diet: green onions; apples; spinach; broccoli; pepper; beets; tomatoes; garlic	include iron, pigments
	exclude fish, meat, offal (for guaiac or benzidine testing)
	Deadline for performing a stool test: x-ray studies; colonoscopy; sigmoidoscopy	contrast agent may distort the result; special devices often damage mucous membranes
	do not eat hard foods; her brushing her teeth	possible injury to the gums, blood getting into the stool

Features of preparing for the Gregersen test

To exclude errors in the results of this method, it is important to strictly follow the diet. Gregersen's reaction to occult blood is sensitive to iron, pigments from food. It is necessary to postpone research for a while under the following circumstances:

• presence of blood in the urine (hematuria);
• menstruation in women;
• hemorrhoids with bleeding;
• periodontal disease;
• indigestion (dyspepsia);
• ruptures, damage as a result of anal sex.

An important role is played by the correct collection of material for analysis. The following conditions must be met:

• carry out hygiene of the genitals and anus;
• collect feces in the morning, before breakfast;
• ingress of water and urine is unacceptable;
• you cannot take biomaterial from the toilet (you need to put an oilcloth on it);
• fragments must be from three places;
• put the stool in a special sterile container;
• deliver to the laboratory within two hours.

Interpretation of stool occult blood test

The doctor interprets the results of the study. The immunochemical test is considered the most accurate, but it is not performed in all laboratories. It takes 1-3 days to conduct and decipher the tests. Experts recommend that, upon receipt of positive and negative results, additional re-examination of stool for the presence of hidden bleeding and diagnosis using instrumental methods.

Negative result

If a small amount of blood enters the intestines, in a healthy person it is decomposed by enzymes. The norm is 0.2 mg of hemoglobin per gram of feces. A negative result confirms the absence of bleeding or dangerous diagnoses in the body, or requires repeated testing when the patient exhibits signs of pathologies.

Positive

If a patient is suspected of having hidden bleeding, a positive test result is possible. It often indicates an early stage of diseases associated with damage to the mucous membranes:

• colorectal cancer;
• peptic ulcer;
• intestinal tuberculosis;
• tumors of the digestive organs;
• helminthiasis;
• pathologies of the esophageal veins;
• hemorrhoids.

Positive reaction to occult blood in a child

When analyzing stool in children, signs of hidden bleeding are sometimes revealed. The reason for a positive reaction depends on age:

False positive and false negative results

Often, stool examinations for the presence of hidden blood loss give ambiguous results - false negative, false positive. In this case, repeated tests must be performed and additional diagnostics carried out. A false positive response is possible in such cases.