Variable test performance seen with FIT for advanced colorectal neoplasia

Fecal immunochemical tests (FITs) have variable sensitivity and specificity for detecting advanced colorectal neoplasia (ACN), according to a study published online Sept. 3 in the Annals of Internal Medicine.

Barcey T. Levy, M.D., Ph.D., from the University of Iowa Carver College of Medicine in Iowa City, and colleagues compared the performance characteristics of five commonly used FITs (with colonoscopy as the reference standard) in a cross-sectional study in three U.S. academic medical centers and affiliated endoscopy units. Participants aged 50 to 85 years completed five different FITs before colonoscopy: four qualitative tests (Hemoccult ICT, Hemosure iFOB, OC-Light S FIT, and QuickVue iFOB) and one quantitative test (OC-Auto FIT). Test performance for ACN, defined as advanced polyps or colorectal cancer (CRC), was the primary outcome.

A total of 3,761 participants were enrolled in the study. The researchers found that 320 participants had ACN (8.5 percent), including nine (0.2 percent) with CRC. Test positivity varied from 3.9 to 16.4 percent across FITs. There was variation observed in the rates of unevaluable FITs, from 0.2 to 2.5 percent. For ACN, the sensitivity and specificity varied from 10.1 to 36.7 percent and from 85.5 to 96.6 percent, respectively. All differences in sensitivity between FITs were statistically significant apart from the difference between Hemosure iFOB and QuickVue iFOB, while all differences in specificity were statically significant. Distal location of ACN was also associated with higher FIT sensitivity.

"Our findings have implications for the benefits and cost-effectiveness of CRC screening using FIT," the authors write.

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