Annual FIT has moderate to high sensitivity and specificity for screening asymptomatic adults

Fecal immunochemical tests (FITs) are effective for screening for colorectal cancer when used annually by average-risk, asymptomatic adults, a meta-analysis found.

Noting that only about 65% of eligible U.S. adults undergo colonoscopy, researchers assessed the ability of FIT to increase screening rates and detect colorectal cancer. They reviewed 31 studies involving 120,255 patients to summarize FIT performance for colorectal cancer, quantify FIT performance characteristics for colon polyps, and identify factors affecting those characteristics. Results from the meta-analysis were published Feb. 26 by Annals of Internal Medicine.

Performance characteristics depended on the threshold for a positive result. A threshold of 10 μg/g resulted in sensitivity of 0.91 (95% CI, 0.84 to 0.95) for colorectal cancer and a negative likelihood ratio of 0.10 (95% CI, 0.06 to 0.19). A threshold of greater than 20 μg/g resulted in specificity of 0.95 (95% CI, 0.94 to 0.96) and a positive likelihood ratio of 15.49 (95% CI, 9.82 to 22.39). For advanced adenomas, sensitivity was 0.40 (95% CI, 0.33 to 0.47) and the negative likelihood ratio was 0.67 (95% CI, 0.57 to 0.78) at 10 μg/g. Specificity was 0.95 (95% CI, 0.94 to 0.96) and the positive likelihood ratio was 5.86 (95% CI, 3.77 to 8.97) at greater than 20 μg/g.

The findings show that single-application FITs have moderate to high sensitivity and specificity for colorectal cancer, depending on the positivity threshold, the study authors said. At a high specificity, FITs are moderately sensitive for colorectal cancer. Although FITs are much less sensitive for advanced adenomas, these lesions rarely transition to cancer, so there could be an opportunity to detect them with programmatic screening before they become cancer, according to the study authors.

Because at-home FITs are easy-to-use, non-invasive, and inexpensive, their adoption could improve lagging colorectal cancer screening rates, especially among vulnerable populations, the authors wrote.

An editorial lamented the fact that colonoscopy is considered the “best/gold standard” screening test when there is little research supporting that, or comparing colonoscopy to less invasive, less expensive tests. Physicians and patients may be unaware that FITs are noninvasive, easy to prepare, inexpensive, and have effectiveness similar to that of colonoscopy when used in a consistently to screen for colorectal cancer, the editorial stated. However, it said, media and health systems continue to promote colonoscopy as the best test for colorectal cancer, despite changes to U.S. screening guidelines.

Physicians should be educated about the advantages of FIT in screening for colorectal cancer, the editorial stated. Changes to insurance coverage could lead to vulnerable populations being more successfully screened.

The editorial stated, “If we hope to achieve national goals for CRC [colorectal cancer] screening, we must learn as much as we can about the screening tests and advocate for funding of comparative studies of available tests and insurance coverage not only for screening colonoscopies but for those done after a positive FIT result.”

An article in the January 2019 ACP Internist looked at ways to increase colorectal cancer screening rates.