Occult Blood
A faecal occult blood test is a stool test that looks for hidden, or occult, blood in the stool. It may be done during a visit with a healthcare provider, or taken at home. One form finds heme and may spot bleeding higher in the gastrointestinal tract, while the faecal immunochemical test is more likely to spot bleeding in the lower gastrointestinal tract, which makes it a more specific test for colorectal cancer screening.
Why it matters: The test may be used when there are symptoms suggesting hidden gastrointestinal bleeding, such as unexplained belly or anal pain, or symptoms of anaemia like fatigue and pallor, and a provider may order one to help confirm or rule out a diagnosis. It is also used as a form of cancer screening. A negative or normal result means no bleeding was detected. A positive result means blood was detected, which could be from several causes: bleeding in the colon does not always mean cancer, and the test can sometimes produce a false positive, which is why a positive result is confirmed rather than acted on alone. This test cannot positively diagnose colon cancer or any other condition. A provider will want to investigate a positive result further, usually with a colonoscopy to look for colon polyps or other causes of bleeding in the lower intestine, or an upper gastrointestinal endoscopy where symptoms or other tests suggest upper gastrointestinal bleeding.
Source · Cleveland Clinic — what it is, why it matters, what moves it, related conditions
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What is Occult Blood?
A faecal occult blood test is a stool test that looks for hidden, or occult, blood in the stool. It may be done during a visit with a healthcare provider, or taken at home. One form finds heme and may spot bleeding higher in the gastrointestinal tract, while the faecal immunochemical test is more likely to spot bleeding in the lower gastrointestinal tract, which makes it a more specific test for colorectal cancer screening.
What might a high or low Occult Blood mean?
The test may be used when there are symptoms suggesting hidden gastrointestinal bleeding, such as unexplained belly or anal pain, or symptoms of anaemia like fatigue and pallor, and a provider may order one to help confirm or rule out a diagnosis. It is also used as a form of cancer screening. A negative or normal result means no bleeding was detected. A positive result means blood was detected, which could be from several causes: bleeding in the colon does not always mean cancer, and the test can sometimes produce a false positive, which is why a positive result is confirmed rather than acted on alone. This test cannot positively diagnose colon cancer or any other condition. A provider will want to investigate a positive result further, usually with a colonoscopy to look for colon polyps or other causes of bleeding in the lower intestine, or an upper gastrointestinal endoscopy where symptoms or other tests suggest upper gastrointestinal bleeding.
What can affect Occult Blood?
It may be higher with: Colon polyps, whose fragile surface blood vessels can break and bleed easily, Anal fissures, Anal sexually transmitted infections, Diverticulosis or diverticulitis, Oesophageal or gastrointestinal varices, Haemorrhoids, Infectious colitis or gastroenteritis, Inflammatory bowel disease, Peptic ulcer disease, NSAIDs including aspirin, naproxen and ibuprofen, which can cause temporary bleeding in the stomach, Blood thinners such as heparin, warfarin or clopidogrel, which make abnormal bleeding more likely.
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