BACKGROUND: Outreach (i.e., to invite those who do not use, or who under use screening services) and inreach (i.e., to invite an existing population who have already accessed the medical system) approaches may influence people to increase their use of screening test; however, whether their outcomes would be equivalent remains unclear. METHODS: A total of 3,363,896 subjects, 50-69 years of age, participated in a colorectal cancer (CRC) screening program using biennial fecal immunochemical tests; 34.5% participated during 2004-2009 when the outreach approach alone was used, and 65.5% participated from 2010-2013 when outreach was integrated with an inreach approach. We compared the outcomes of the two approaches in delivery of screening services. RESULTS: Coverage rates increased from 21.4% to 36.9% and the positivity rate increased from 4.0% to 7.9%, while referral for confirmatory diagnostic examinations declined from 80.0% to 53.3%. The first period detected CRC in 0.20% of subjects screened, with a positive predictive value (PPV) of 6.1%, and the second detected CRC in 0.34% of subjects, with a PPV of 8.0%. After adjusting for confounders, differences were observed in the PPV for CRC (adjusted relative risk, 1.50; 95% confidence interval [CI], 1.41-1.60), cancer detection rate (1.20; 95% CI, 1.13-1.27), and interval cancer rate (0.72; 95% CI, 0.65-0.80). When we focused on the comparison between two approaches during the same study period of 2010-2013, the positivity rate of fecal testing (8.2% vs. 7.6%) and the PPV for CRC detection remained higher (1.07; 95% CI, 1.01-1.12) in subjects who were recruited from the inreach approach. CONCLUSIONS: Outcomes of screening were equivalent or better after integration of outreach and inreach approaches. IMPACT: The results will encourage makers of health-care policy to adopt the integration approach to deliver screening services.
