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To review the evidence on fecal DNA testing to screen for colorectal cancer in adults at average risk for colorectal cancer.
We searched MEDLINE, Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials, Database of Abstracts of Reviews of Effects, and the Health Technology Assessments Database from 2000 through August 11, 2011 and grey literature including recent conference abstracts, regulatory documents, unpublished information from the manufacturer, and expert suggestions.
Two investigators independently reviewed all abstracts and full-text articles against a set of a priori inclusion criteria and assessed the quality of included articles using established criteria. Disagreements were resolved through consultation of a third investigator. We evaluated and summarized clinical and methodological characteristics and internal and external validity of studies. Finally, we assessed the overall strength of evidence for each outcome based on risk of bias, consistency, directness, and precision of the evidence.
Despite the availability of numerous excluded initial validation studies of fecal DNA testing, we found only three studies that examined the test accuracy of fecal DNA testing in screening populations. Initial validation studies were excluded due to their use of highly selected patient populations. Two fair-quality diagnostic accuracy studies (n=5004) evaluating a multi-marker fecal DNA found differing sensitivities to detect CRC (25 percent [95% CI, 5 to 57 percent] versus 51.6 percent, [95% CI, 34.8 to 68.0]). Sensitivity for advanced adenomas was similarly low in both studies. Another small study and a subset analysis of one of the larger studies were both poor quality and evaluated different tests. We found no studies that specifically evaluated the harms of fecal DNA testing. While three poor-quality analytic validity studies showed that technological advances can improve the analytic sensitivity of assays, it is unclear if these advances are applicable to the currently available test. Six fair-to poor-quality studies that evaluated acceptability found that fecal DNA testing is generally acceptable, although an important test attribute for acceptability appears to be the test's accuracy (which is yet unknown). No studies have evaluated the relative acceptability of fecal DNA tests to FIT tests.
Fecal DNA tests have insufficient evidence about its diagnostic accuracy to screen for colorectal cancer in asymptomatic, average-risk patients. There is also insufficient evidence for the harms, analytic validity, and acceptability of testing in comparison to other screening modalities. Existing evidence has little or no applicability to currently available fecal DNA testing.