Positive predictive values of fecal immunochemical tests used in the STOP CRC pragmatic trial

Annual fecal immunochemical testing (FIT) is cost-effective for colorectal cancer (CRC) screening. However, FIT positivity rates and positive predictive value (PPV) can vary substantially, with false-positive (FP) results adding to colonoscopy burden without improving cancer detection. Our objective was to describe FIT PPV and the factors associated with FP results among patients undergoing CRC screening. In an ongoing pragmatic clinical trial of mailed-FIT outreach, clinics delivered one of three FIT brands (InSure, OC-Micro, and Hemosure). Patients who had a positive FIT result and a follow-up colonoscopy were included in this analysis (N = 1130). Patients' demographic and medical histories were abstracted from electronic health records (EHR). Associations with a FP result (ie, a positive FIT result with no evidence of advanced neoplasia during follow-up colonoscopy) were evaluated for FIT brand and patient factors using mixed-effects multivariable logistic regression. The mean proportion of FIT-positive results ranged from 8% in centers using the OC-Micro test to 21% for Hemosure. PPVs for advanced neoplasia were 0.30 to 0.17, respectively (P for χ²  = 0.08). In multivariable-adjusted models, use of Hemosure was associated with greater odds of a FP result than OC-Micro (OR = 2.00, 95% CI: 0.47-8.56) or InSure (OR = 1.72, 95% CI: 0.44-6.68). However, only female sex (OR = 1.58, 95% CI: 1.19-2.10) and history of a colorectal condition (OR = 2.17, 95% CI: 1.13-4.15) were significantly associated with FP. In conclusion, FIT positivity varied by brand, and FP results differed by patient factors available through the EHR. These results can be used to minimize the frequency of FP results, reducing patient distress and colonoscopy burden.