Background: Guidelines now recommend initiating colorectal cancer (CRC) screening at age 45 years rather than 50 years, but little is known about screening completion and yield among people aged 45 to 49 years.
Objective: To evaluate fecal immunochemical test (FIT) completion and yield in patients aged 45 to 49 versus 50 years.
Design: Retrospective cohort study.
Setting: Kaiser Permanente Northern California, Washington, and Colorado.
Patients: Those distributed a FIT kit during January to September 2022.
Measurements: FIT completion within 3 months, FIT positivity, receipt of colonoscopy within 3 months after a positive FIT result, and colonoscopy yield.
Results: A total of 267 732 FIT kits were distributed: 213 928 (79.9%) to patients aged 45 to 49 years, and 53 804 (20.1%) to those aged 50 years. Overall, FIT completion was slightly higher in patients aged 45 to 49 years (38.9% vs. 37.5%; adjusted risk ratio [aRR], 1.05 [95% CI, 1.04 to 1.06]), although at Colorado, those aged 45 to 49 years were substantially less likely to complete a FIT (30.7% vs. 40.2%; aRR, 0.77 [CI, 0.73 to 0.80]). Overall, FIT positivity was lower in patients aged 45 to 49 years (3.6% vs. 4.0%; aRR, 0.91 [CI, 0.84 to 0.98]), and receipt of colonoscopy after a positive FIT result was similar between groups (64.9% vs. 67.4%; aRR, 1.00 [CI, 0.94 to 1.05]). Adenoma detection was lower in the younger group (58.8% vs. 67.7%; aRR, 0.88 [CI, 0.83 to 0.95]). Yields were similar for adenoma with advanced histology (13.2% vs. 15.9%; aRR, 0.86 [CI, 0.69 to 1.07]), polyp with high-grade dysplasia (3.4% vs. 5.1%; aRR, 0.68 [CI, 0.44 to 1.04]), sessile serrated lesion (10.3% vs. 11.7%; aRR, 0.92 [CI, 0.71 to 1.21]), and CRC (2.8% vs. 2.7%; aRR, 1.10 [CI, 0.62 to 1.96]).
Limitation: The small number of neoplasia events contributed to wide CIs.
Conclusion: Similar FIT completion and yield rates in people aged 45 to 50 years support initiation of CRC screening at age 45 years.
Primary funding source: Kaiser Permanente Sidney R. Garfield Memorial Fund.