Effect of Verification Bias on the Sensitivity of Fecal Occult Blood Testing: a Meta-Analysis
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There is controversy regarding the sensitivity of fecal occult blood tests (FOBT) for detecting colorectal cancer. Many of the published studies failed to correct for verification bias which may have increased the sensitivity.
A meta-analysis of published studies evaluating the sensitivity and specificity of chemical-based FOBT for colorectal cancer was performed. Studies were included if both cancer and control subjects underwent confirmatory testing. We also included studies that attempted to correct for verification bias by either performing colonoscopy on all subjects regardless of the FOBT result or by using longitudinal follow-up. We then compared the sensitivity, specificity, and other diagnostic characteristics of the studies that attempted to correct for verification (n = 10) vs. those that did not correct for this bias (n = 19).
The pooled sensitivity of guaiac-based FOBT for colorectal cancer of studies without verification bias was significantly lower than those studies with this bias [0.36 (95% CI 0.25-0.47) vs. 0.70 (95% CI 0.60–0.80), p = 0.001]. The pooled specificity of the studies without verification bias was higher [0.96 (95% CI 0.94–0.97) vs. 0.88 (95% CI 0.84–0.91), p < 0.005]. There was no significant difference in the area under the summary receiver operating characteristic curves. More sensitive chemical-based FOBT methods (e.g., Hemoccult® SENSA®) had a higher sensitivity but a lower specificity than standard guaiac methods.
The sensitivity of guaiac-based FOBT for colorectal cancer has been overestimated as a result of verification bias. This test may not be sensitive enough to serve as an effective screening option for colorectal cancer.
KEY WORDSfecal occult blood guaiac colorectal cancer summary receiver operating characteristic curve meta-analysis
Department of Veterans Affairs.
Conflict of interest
Both authors had access to the data and a role in writing the manuscript.
- 3.Centers for Disease Control and Prevention. Use of colorectal cancer tests-United States, 2002, 2004, and 2006. MMWR Morb Mortal Wkly Rep. 2008;57:253–8.Google Scholar
- 18.Dinnes J, Deeks J, Kirby J, Roderick P. A methodological review of how heterogeneity has been examined in systematic reviews of diagnostic test accuracy. Health Technol Assess. 2005;9:1–113.Google Scholar
- 65.Cheng T-I, Wong J-M, Hong C-F, et al. Colorectal cancer screening in asymptomaic adults: comparison of colonoscopy, sigmoidoscopy and fecal occult blood tests. Taiwan Yi Xue Hui Za Zhi. 2002;101:685–90.Google Scholar
- 69.Towler B, Irwig L, Glasziou P, Kewenter J, Weller D, Silagy C. A systematic review of the effects of screening for colorectal cancer using the faecal occult blood test, hemoccult. Br Med J. 1998;317:559–65.Google Scholar
- 71.Screening for colorectal cancer: U.S.Preventive Services Task Force recommendation statement. Ann Intern Med 2008;149:627-37.Google Scholar
- 72.Levin B, Lieberman DA, McFarland B, et al. Screening and surveillance for the early detection of colorectal cancer and adenomatous polyps, 2008: a joint guideline from the American Cancer Society, the US Multi-Society Task Force on Colorectal Cancer, and the American College of Radiology. CA Cancer J Clin. 2008;58:130–60.CrossRefPubMedGoogle Scholar