Avoid a false-positive result

Postpone the test if you're menstruating or have bleeding hemorrhoids, bleeding gums, or blood in your urine. That blood can sometimes reach the stool, setting off a false alarm.

Avoid red meat, which is loaded with blood byproducts, during the test period and for two days before it. Follow the same precaution for raw fruits and vegetables, particularly cauliflower, horseradish and other radishes, melons, and turnips. Those foods contain peroxidase, which can spark a positive chemical reaction.

Avoid aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen (Advil), ketoprofen (Orudis KT), and naproxen (Aleve), for a week before the test, since they can cause gastrointestinal bleeding.

TO minimize the chance of a false-negative result--failure to detect a worrisome growth--take these steps before and during the test period:

Eat foods high in fiber, which may rub against any growths, perhaps encouraging them to bleed.

Don't take vitamin-C pills or eat foods that are rich in the vitamin, which can prevent the chemical test from detecting blood.

If either the stool test or sigmoidoscopy reveals a problem, you need to undergo colonoscopy, the more extensive version of sigmoidoscopy that allows the doctor to view the entire five-foot length of the colon and to remove any polyps and find early cancers. Either colonoscopy or a double-contrast barium enema should be repeated in three years.

Last updated Nov 26/06