Positive predictive value of fecal immunochemical test for high-risk colonic adenomas and carcinoma: A health maintenance organization cohort screening study in Lebanon

Background and study aims: Fecal Immunochemical Test (FIT) is one of the leading modalities for colorectal cancer screening. Studies show that FIT is highly sensitive for the detection of colorectal cancer (CRC) but not similarly accurate for detection of pre-cancerous advanced adenomas (AA). We studied the performance metrics of FIT for the detection of CRC and AA in ahealth maintenance organization (HMO) cohort screening program.

Patients and methods: Retrospective cohort study of asymptomatic persons of screening age belonging to a HMO. Endoscopy and pathology reports of those who tested positive were used to calculate the positive predictive value (PPV) of FIT, and characterize endoscopic findings on colonoscopy.

Results: Between 1995 and 2017, 3000 persons had screening fecal occult testing as part of their Employee Health Care plan. Of those, 150 had a positive qualitative FIT (cutoff 10 µg hemoglobin/g feces). All underwentcolonoscopy, and median time to colonoscopy was 27 days. 4 (2.6%) had carcinoma(2 stage IIIA and 2 stage IIIB), 106 (70.6%) had adenomas of which 40 (26.6% of the total cohort) had advanced adenomas (≥1 cm, villous features, or high-grade dysplasia) giving a PPV for AA and carcinoma of 29% and 3% respectively. When stratified by age, the PPV of AA; carcinoma was [50-59 (21.7%; 0.0%)], [60-69 (14.6%; 4.2%)], [70-79 (42.6%; 2.1%)], [80-89 (33.3%; 11.1%)].

Conclusion: The performance characteristics of FIT testing are acceptable for population screening in resource-limited settings. The resultsof this study are helpful when discussing expectations prior to colonoscopy in people with positive FIT.