Effect of false-positives and women's characteristics on long-term adherence to breast cancer screening.

False-positive results may influence adherence to mammography screening. The effectiveness of breast cancer screening is closely related to adequate adherence among the target population. The objective of this study was to evaluate how false-positives and women's characteristics affect the likelihood of reattendance at routine breast cancer screening in a sequence of routine screening invitations. We performed a retrospective cohort study of 1,371,218 women aged 45-69 years, eligible for the next routine screening, who underwent 4,545,346 screening mammograms from 1990 to 2006. We estimated the likelihood of attendance at seven sequential screening mammograms. Multilevel discrete time hazard models were used to estimate the effect of false-positive results on reattendance, and the odds ratios (OR) of non-attendance for the women's personal characteristics studied. The overall reattendance rate at the second screening was 81.7% while at the seventh screening was 95.6%. At the second screening invitation reattendance among women with and without a false-positive mammogram was 79.3 vs. 85.3%, respectively. At the fourth and seventh screenings, these percentages were 86.3 vs. 89.9% and 94.6 vs. 96.0%, respectively. The study variables associated with a higher risk of failing to participate in subsequent screenings were oldest age (OR = 8.48; 95% CI: 8.31-8.65), not attending their first screening invitation (OR = 1.12; 95% CI: 1.11-1.14), and previous invasive procedures (OR = 1.09; 95% CI: 1.07-1.10). The risk of non-attendance was lower in women with a familial history of breast cancer (OR = 0.97; 95% CI: 0.96-0.99), and those using hormone replacement therapy (OR = 0.96; 95% CI: 0.94-0.97). In conclusion, reattendance was lower in women with false-positive mammograms than in those with negative results, although this difference decreased with the number of completed screening participations, suggesting that abnormal results in earlier screenings more strongly influence behavior. These findings may be useful in providing women with accurate information and in improving the effectiveness of screening programs.