FALSE POSITIVE FECAL OCCULT BLOOD TESTS FROM RED MEAT.

One drawback of fecal occult blood testing is that ingestion of red meat can cause false-positive results. In this study, Feinberg and colleagues determined how long after eating red meat false positives may occur. Forty-six young, healthy volunteers consumed about 400 grams of cooked red meat daily for 3 days. Stool samples were then tested on 7 consecutive days using each of four commercial tests (Hemoccult II, Hemoccult SENSA, HemoQuant, and HemeSelect).

The first three tests detected occult blood during the first 3 days of testing; positivity rates were 15 to 46 percent on day 1, 5 to 42 percent on day 2, and 5 to 14 percent on day 3. In contrast, HemeSelect tests were negative during all 7 days. This result was not unexpected, since Hem…