How are fecal occult blood tests performed?

In the lab: Great question. A great way to screen for intestinal cancer as cancers cause small amounts of bleeding, which is then passed in the feces. A less sensitive chemical method and more accurate immuno method can be used. Not all cancers will leak blood, blood in feces is not always cancer and other substances can have false results. Ask your doc about colonoscopy if >50 or family history of cancer.

Varies: Usually it requires a sample of the stool and then exposing it to a reagent either chemical or immunologic and comparing the results to a control sample. Some can be done at home and others require a sample obtained in the doctors office. The sensitivity and specificity of the result depends upon the type of test and how it is performed.