Preparation for analysis of latent blood in feces

Contents
  • Indications for the purpose of the analysis
  • Types of tests
  • Preparation for the analysis by Gregersen
  • Collection of stool for the study
  • False results
  • Video on the topic

The occult blood test is one of the laboratory tests that allow to diagnose the internal bleeding in a high degree of probabilityone of the departments of the digestive tract. Special attention needs preparation for the analysis of feces for latent blood, since in the absence of it or incorrectly, false positive results can be obtained.

Indications for the appointment of the

test The examination of feces for the blood latent in it is prescribed in the following patient complaints:

  • persistent / recurring abdominal pain;
  • frequent symptoms of dyspepsia disorder - nausea, vomiting, heartburn;
  • regular diarrhea;
  • unexplained weight loss.

Testing of feces on the blood present in their composition is assigned to confirm the diagnosis, for example, peptic ulcer or erosive gastritis. The general purpose of the analysis is the detection of latent damage to the mucous membranes of the stomach or intestinal tract.

Types of tests

In the presence of bleeding areas of the mucosa in human feces, blood may be present. If the place of bleeding has become a stomach or 12-duodenal ulcer, the fecal masses get a dark red color. If the surface of the large intestine is damaged, they become scarlet. But not always in the stool of a person you can consider the admixture of blood. Very often small ulcers bleed only periodically.

Laboratory testing of feces for occult blood allows one to determine even the minimum amount of hemoglobin contained in it.

Two studies are being carried out:

  • by the Gregersen method( benzidine test);
  • immunochemical test.

Gregersen's test is quite informative, but only if the patient is carefully prepared

Gregersen's method allows you to detect even a minimal concentration of hemoglobin. This is both a virtue and a drawback of the method. Benzodin stains the molecules of iron in blue, but it reacts to both human and extraneous hemoglobin( present in meat).

The immunochemical method is more accurate. Its significant drawback is that it is quite lengthy in time. The test results will be received only two weeks after the material is submitted for the study. Therefore, in most cases, the delivery of feces for analysis by the method of Gregersen.

Preparation for Gregersen analysis

To get the most reliable results, it is necessary to properly prepare for the feces delivery. Recommendations will be as follows:

  1. One week before the planned delivery, it is necessary to stop taking such drugs as laxatives, bismuth and iron-containing, anti-inflammatory non-steroid agents. It is forbidden to use acetylsalicylic acid and its containing medicines.
  2. It is necessary to abandon the introduction of rectal suppositories.
  3. Clipping is forbidden.
  4. Before analyzing feces for latent blood - for two days before delivery - you need to exclude any instrumental tests of the digestive tract. During the study, the mucosa can be accidentally damaged. Excreted blood can provoke false positive results.
  5. For a few days before the excrement is collected, the teeth should be discarded. Even a small amount of blood released by gum damage can get into the stomach. And this hemoglobin is also able to negatively affect the end result.
Before the analysis, the patient will be advised to follow a special diet. Its duration is 72 hours.

The main point of preparation for delivery analysis is strict adherence to the

diet. The patient's diet should completely exclude products with high iron content. Fecal collection should be preceded by a failure:

  • from apples;
  • of cucumbers;
  • of white beans;
  • spinach;
  • horseradish;
  • cauliflower;
  • meat and fish dishes;
  • by-products;
  • vegetables are green.

Ideally, in order not to make a mistake with the menu, doctors recommend that in the preparation for the delivery of stool, adhere to a dairy diet. The ration may also include:

  • potatoes;
  • bread;
  • porridge( except - buckwheat, oatmeal, yak, lentils, peas).

Non-compliance with recommendations will lead to an error and reoccurrence of feces to the study or the appointment of more serious tests.

Fecal collection for the

study Even carefully prepared preparation will be completely useless if the biological material is not properly collected.


For transportation of feces to the laboratory there are special containers - they are sterile and guarantee the biological purity of the collected excrement

How to properly pass the feces? To obtain a test material, the following recommendations should be observed:

  1. To collect excrement, use a sterile container. It can be purchased at any pharmacy. The set includes a jar with a lid and a special spoon.
  2. Beforehand, you need to empty the bladder. Then lay in the toilet bowl oilcloth.
  3. After bowel movement it is necessary to take a fence of three portions of stool from different places.

The material must be delivered to the laboratory within the next three hours. He is not subject to storage.

False results of

Failure to comply with the preparation rules before the delivery of stool can lead to erroneous results. They can be both false positive and false negative.


The main cause of false positive tests indicating the presence of internal bleeding is incorrect preparation

False positive results are found quite often. The reason is the man's disregard for the preparatory stage. In this case, the test shows a high hemoglobin content in the absence of internal bleeding. Distort the final results can only one apple, eaten a day before the delivery of biological material.

Properly prepared for the study of feces for occult blood in many cases avoids the very unpleasant procedure of a colonoscopy. The technique is an examination of the intestine by introducing the equipment through the anus.