Fecal immunochemical testing more sensitive than guaiac testing

Clinical Question

Are fecal immunochemical tests better than newer guaiac tests in detecting colorectal adenomas and carcinomas?

Bottom Line

In this study, fecal immunochemical testing was more sensitive than newer guaiac testing and had comparable specificity in the detection of colorectal cancers and adenomas. I'd like to see a more rigorous study without verification bias before recommending the routine use of fecal immunochemical testing. (LOE = 3b)

Reference

Allison JE, Sakoda LC, Levin TR, et al. Screening for colorectal neoplasms with new fecal occult blood tests: update on performance characteristics. J Natl Cancer Inst 2007;99(19):1462-1470.  [PMID:17895475]

Study Design

Cross-sectional

Funding

Other

Setting

Outpatient (any)

Synopsis

This study included nearly 6000 patients who were 50 years and older, enrolled in a health maintenance organization, and at average risk for developing colorectal cancer. Patients were invited to participate or were referred by their primary care physicians. Each patient received 3 cards for stool testing. The cards were designed to allow for testing using a sensitive guaiac test or a fecal immunochemical test. Laboratory technicians developed each test individually and were masked to the results of the other tests on the card. Unfortunately, the gold standard of colonoscopy was not uniformly applied to all patients. Only patients with a positive result on any of the tests underwent colonoscopies. Everybody else received sigmoidoscopy. This is called verification bias and it tends to overestimate the sensitivity. If the authors' data are true, fecal immunochemical testing is more sensitive than guaiac testing and has comparable specificity in detecting cancers and adenomas. Whether looking for cancers or adenomas, all the tests were quite specific (all more than 90%), meaning that if the test result was positive, there was a high likelihood of detecting an abnormality. Although the immunochemical tests were more sensitive in detecting cancers (82% vs 64%), none of the tests were very sensitive in the detection of adenomas (30% and 41%, respectively).