Fecal immunochemical test (FIT)

The fecal immunochemical test (FIT) searches for traces of blood in the stool (just like FOBT), but this time using techniques of immunochemistry instead of chemicals. 

This means using antibodies that specifically bind to human hemoglobin (a protein that exists in red blood cells) or substances that result from its degradation. 

The samples are maintained at -5 ° C to avoid deterioration. 

FIT is being studied as an alternative screening method for FOBT

This because antibodies are extremely specific to what they bind, so there are no false positive results due to cross-rea,ction with foods and vitamin supplements. FIT also require fewer samples.

FOBT, if a test is positive, colonoscopy is used to know the causes of the bleeding.

However, because hemoglobin (the target of the antibodies) is rapidly digested in the stomach and small intestine, FIT is more specific for colon bleedings.

Like FOBT, FIT does not detect small tumors or tumors that do not bleed.

There is a yet another test done on stool samples, it is less used but can detect tumors: the Fecal DNA test