Fecal immunochemical test

Last revised by Daniel J Bell on 4 Mar 2021

A fecal immunochemical test (FIT) is a test for human hemoglobin in stool as a screening tool for colorectal carcinoma. It is considered a better test than the traditional guaiac fecal occult blood test (gFOBT) which cannot distinguish human blood from food-derived sources. 

A fecal immunochemical test uses an antibody-based assay for the globin component of the hemoglobin molecule 2. The laboratory assay employs an automated immunoturbidometric test. Point of care assays use a form of immunochromatography 2.

There are a very large number of fecal immunochemical tests on the market and they are not equivalent in their accuracy 2.

Clearly, depending on the level of fecal hemoglobin used as a cut-off value, the sensitivity and specificity of the fecal immunochemical test will vary. 

The guaiac-based test has been in regular clinical use for a very long time, first being developed in the 1860s. Fecal immunochemical tests were introduced in the 1970s 2.

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