Fecal occult blood testing as a diagnostic test in symptomatic patients is not useful: a retrospective chart review

The fecal occult blood test (FOBT) is a screening tool designed for the early detection of colorectal cancer in primary care. Although not validated for use in hospitalized patients, it is often used by hospital physicians for reasons other than asymptomatic screening.

To profile the in-hospital use of the FOBT and assess its impact on patient care.

Patient charts were retrospectively reviewed for all FOBTs conducted over a three-month period in 2011 by the central laboratory supporting the three acute care campuses of Hamilton Health Sciences (Hamilton, Ontario).

A total of 229 patients underwent 351 tests; 52% were female and the mean age was 49 years (range one to 104 years). A total of 80 (34.9%) patients had at least one positive test. The most common indications for testing were anemia (51.0%) and overt gastrointestinal bleeding (19.2%). Only one patient had testing performed for asymptomatic colorectal cancer screening. In only 20 (8.7%) cases medications were modified before testing and diet was modified in only 21 (9.2%) cases. Most patients (85.2%) were taking one or more medications that could result in a false-positive result. Only 18 (7.9%) patients had a digital rectal examinations documented, of which seven were positive. All patients with a positive digital rectal examination underwent endoscopic procedures that revealed a source of bleeding. Among 44 patients with overt gastrointestinal bleeding, 12 (27.3%) had endoscopic investigations delayed to await results of the FOBT. Four patients were referred despite a negative FOBT due to a high degree of suspicion of gastrointestinal bleeding.

The FOBT is often used inappropriately in the hospital setting. Confounding factors, such as diet and medication use, which may lead to false positives, are often ignored. Use of the FOBT in-hospital may lead to inappropriate management of patients, increased length of stay and increased direct medical costs. Use of the FOBT should be limited to validated indications only.