Are occult blood tests for colon cancer reliable?

Not really: The sensitivity of occult blood test is very low -about 20-25% if it is done only once. If it is done in 3 separate occasions- the sensitivity of the test to check for GI bleeding will be higher up to 90%. However, the test's accuracy for colon cancer is not high as GI bleeding can be caused by so many things-hemorrhoids, avm, gastric ulcer etc. Colonsocopy needs to be done if occult blood is +.

Screening: It is a good start specially of yo had before and they were normal.