In this era of skyrocketing health-care costs, how many serial stool guaiac tests would a patient have to have in order to obtain results equivalent to screening colonoscopy for colorectal cancer?
—Peter Brassard, MD, East Providence, R.I.

Hemoccult (or guaiac) testing is the easiest and cheapest screening test, but sensitivity for a single specimen is 40%, so guaiac testing will miss 60% of cancers. The American Gastroenterological Association recommends testing two samples from three consecutive stools annually. Repeating guaiac testing annually may eventually detect up to 92% of cancers but over several years. Colonoscopy is the most expensive and riskiest screening test, but it has a sensitivity of nearly 100%. While any screening is better than none, no number of stool guaiac tests will match the sensitivity of colonoscopy.
—Christina M. Surawicz, MD (109-2)