Why is an occult blood test needed?

If you suspect intestinal problems during diagnosis, it is possible to do with a little blood. Moreover, in the literal sense – you just need to do the appropriate laboratory test. The analysis of feces for occult blood has been widely used in medicine for more than half a century, since it is a convenient and simple way to identify imperceptible blood loss to the intestine. Studies have shown that colorectal cancer mortality, for example, can be reduced by up to 30% just by doing this analysis every year.

But this test has limitations – before you take it, you need to observe special for 3-4 days to exclude low-roasted meat, uncooked smoked sausages, since the test system can “see” animal hemoglobin in a stool sample and give the so-called “false positive” result.

Start simple

The presence of clearly visible blood in the stool does not necessarily mean something terrible. Most often, it indicates a banal hemorrhoid or anal fissure. But it is also impossible not to pay attention to the symptom, because, in particular, this is how colorectal cancer can manifest itself. True, usually blood in feces with such a disease is not visible, since it is excreted in small quantities and, moreover, in the higher parts of the intestine. Therefore, as a rule, it cannot be detected with the naked eye. And even with a microscopic examination, it is often not visible. Therefore, it can only be found by laboratory means. A sensitive and specific test for transferrin and fecal hemoglobin is now widely used. The study of feces for occult blood is based on the determination of human hemoglobin and transferrin proteins in this biomaterial. And when latent blood is found in the feces, it is advisable to do a colonoscopy with these tests.

Panic aside!

You should not panic after receiving a positive result of such a test. A positive test result is a reason for additional examination. In addition to cancer of the colon and rectum, the appearance of blood in the feces may be other reasons: also gastric ulcer and duodenal ulcer, ulcerative colitis, erosive esophagitis, parasitic infection and others.

The importance of research increases if it is done not occasionally, but regularly – once a year. This annual analysis is especially important for patients over the age of 40.

Preparation is serious business

A fissured anal canal or hemorrhoids can result in fresh blood in the stool that is visible to the naked eye. Fresh blood may not test positive for this test. The test system is configured in such a way that it does not respond to the presence of erythrocyte blood cells, but to proteins that fall out of blood cells during the breakdown of hemoglobin. This is what gives us the opportunity to see the already changed blood, and not fresh, which is visible anyway. The test allows you to suspect the presence of a source of bleeding throughout the entire gastrointestinal tract.

But the main thing is that the stool should be collected naturally, without the use of laxatives (no matter what – in the form of drugs or enemas). Another essential requirement is to prevent urine and water from entering the collected feces. If X-ray diagnostics of the gastrointestinal tract was carried out, then the analysis can be carried out only after 2-3 days. And after carrying out instrumental studies of the gastrointestinal tract, you need to wait two weeks.

As for adhering to a special diet before taking the test, today there is no such need anymore. The test is carried out by a high-precision immunochromatographic method using specific bodies for hemoglobin https://en.wikipedia.org/wiki/Hemoglobin and transferrin, thanks to which no dietary restrictions need to be observed.