Q: Are the FIT stool tests sold in drugstores and online a good screening option for colorectal cancer?
A: Most experts advise not using an over-the-counter stool test to screen for colorectal cancer. Rather, you should ask your doctor to provide you with one of the fecal immunochemical tests (FITs) recommended in the latest guidelines on screening from the U.S. Preventive Services Task Force (USPSTF).
Unlike older guaiac-based stool tests, FITs identify antigens in stool that indicate the presence of human blood originating in the colon or rectum; the results can’t be thrown off by food or medication. If blood is detected, a colonoscopy will be required. Annual FIT is a good screening option, according to a recent consensus statement from the U.S. Multi-Society Task Force, which includes the major gastroenterological associations. (Another stool test, called Cologuard, uses both a FIT and a DNA test—see A New Screening Test for Colon Cancer).
However, though they have been “FDA-cleared,” FIT tests sold directly to consumers in drugstores or online have not been adequately evaluated for quality and efficacy in large average-risk populations.
According to the USPSTF, “the OC FIT-CHEK family of FITs (Polymedco)—which include the OC-Light and the OC-Auto—have the best test performance characteristics.” Used by many large medical groups such as Kaiser Permanente and the Veterans Health Administration, these FITs are not sold directly to consumers. The stool samples are collected by patients and sent to a qualified lab for automated development and interpretation.
By the way, don’t believe claims in ads or on packages that FIT tests can diagnose diverticulitis, irritable bowel syndrome, or colitis.