Reviewers: John Han-Chih Chang, MD and Kenneth Blank, MD
Source: New England Journal of Medicine, July 16, 1998, 339 (3):153
A commonly used screening method for colon cancer is the use of occultblood tests. Occult blood testing can be performed by patients at home.A stool sample is placed on a card, which turns blue if blood is presentin the stool, and remains brown if not. These cards are widely used.Fortunately, the large majority of patients whose cards turn blue do nothave a cancer, but rather a benign cause for the blood in thestool. Unfortunately, all patients who have a positive occult test mustundergo an extensive and costly work-up to ensure the absence of cancer.
A study published in the July 16, 1998 New England Journal of Medicineexamines what percentage of patients with positive occult tests indeed havecancer. Researchers at the Duke University Medical Center prospectivelystudied all patients who were referred for work-up of positive occultblood tests over a 30-month period. All patients underwent colonoscopyand esophagogastrostomy. 248 patients were studied, almost half werewomen.
One-half of the patients were found to have a cause of theirbleeding. The most common causes were benign colon polyps (29 patients),inflammation of the swallowing tube(23), stomach ulcer (14), coloncancer (13), stomach inflammation (12), duodenal ulcer(10), coloninflammation (5) and vascular abnormality (5).
Several conclusions can be drawn from this study: positive occult stooltests are rarely due to cancer (only 5% of patients in this study hadcolon cancer); in one-half the patients no cause of the occult blood wasdetermined; in patients for whom a cause was found, the most commoncauses of the positive test is from inflammation (esophagitis, gastritisor colitis- 16%) and the single most common cause was benign polyps(adenomas) in the colon.