Occult blood (haemoglobin, stool)

Detection of invisible traces of blood in stool via the faecal immunochemical test (FIT). It mainly detects bleeding from the large intestine and rectum; a positive result is clarified by a doctor, usually by colonoscopy.

What occult blood shows

Small bleeds from the gut lining are often not visible to the naked eye, because the blood is distributed and diluted in the stool. The faecal immunochemical test (FIT) uses antibodies to recognise the protein part of human haemoglobin. Blood from the stomach and upper small intestine is largely digested on the long way through the gut; the test therefore mainly detects bleeding from the large intestine and rectum. Because it only recognises human haemoglobin, meat and other foods do not change the result. Small bleeds often occur intermittently rather than continuously.

Occult blood not detectable – what does it mean?

This is the normal case: the sample tested contained no human haemoglobin in a detectable amount, so the lining of the large intestine was not bleeding measurably at the time of sampling. Because bleeding can occur intermittently, the result applies to the sample tested.

Occult blood detected – what happens in the body?

A positive result shows that blood is leaking into the gut somewhere in the lower digestive tract. This happens when the lining is injured or inflamed or small vessels at the surface tear – for example with haemorrhoids, anal fissures, inflammation of the gut lining, gut infections or diverticula. Painkillers from the NSAID group and anticoagulant medications make such bleeding more likely. If a small blood loss continues over a longer period, the body also loses iron along with the haemoglobin: the iron stores empty, and iron-deficiency anaemia with exhaustion and pallor can develop. A positive result is clarified by a doctor, usually by colonoscopy.

The interpretation is given in your report.