Background: The Ontario Breast Screening Program (OBSP) is a population-based breast screening programme, not requiring physician referral. OBSP invites women by mail to book their next screens. However, women who do not participate in the OBSP, may be referred by physicians to non-OBSP mammography facilities, which do not remind women to book their next screen.
Methods: We identified women without breast cancer prior to June 30, 2011, having bilateral mammography (M) during a baseline period at age 50 - 69 at OBSP or non-OBSP facilities, and during a re-exposure period, at the same facility type. We used a case-control design to study the association of facility type and having M during an outcome period. Cases were women failing to receive the outcome M. Controls were matched by age, census tract, and socioeconomic status. Exposure was baseline facility type. Covariates were comorbidity, residential mobility, and primary care physician (PCP) characteristics. Conditional logistic regression analysis was performed.
Results: Cases were less likely to have been screened at OBSP facilities. Failure to receive the outcome M was associated with having moved after re-exposure M (OR = 1.61, 95% confidence interval (CI) 1.52, 1.71), having a male PCP (OR = 1.05, 95% CI 1.02, 1.05), or a higher Charlson score (OR = 1.06 per unit increase, 95% CI 1.03, 1.09). Having re-exposure M at an OBSP facility (OR = 0.18, 95% CI 0.18, 0.19)., having a Canadian trained PCP (OR = 0.83, 95% CI 0.8, 0.87), and having a PCP one year after the re-exposure M (OR = 0.81, 95% CI 0.68, 0.97) were protective against failure to receive the outcome M.
Conclusions: The OBSP, not requiring physician referral, and inviting women by mail to book their next screen, is associated with a lower probability of failure to reattend for subsequent screening than screening by PCP referral to non-OBSP facilities.