Cumulative false positive recall rate and association with participant related factors in a population based breast cancer screening programme.

STUDY OBJECTIVE To investigate the cumulative false positive recall rate throughout the period of participation in a population based breast cancer screening programme and to examine its association with women related factors. DESIGN Analysis of a database to estimate the cumulative false positive recall rate after 10 biennial mammograms in a cohort of women. Cumulative risk after 10 rounds was calculated by projecting forward the information available on the four rounds. Logistic regression was used to evaluate the association between the cumulative risk of false positive recall and women related factors. SETTING Population based breast cancer screening programme in Barcelona City (Spain). PARTICIPANTS 8502 women aged 50-69 years who participated in four consecutive screening rounds. Eligible women had received a mammogram in the first screening round between 1 December 1995 and 31 December 1996. MAIN RESULTS The false positive recall rate in the first screening for women who entered the screening programme at the age of 50-51 years was assessed at 10.6% (95% CI 8.9, 12.3). In the second screening this risk decreased to 3.8% (95% CI 2.7, 4.9) and remained almost constant in subsequent rounds. After 10 mammograms, the cumulative false positive recall rate was estimated at 32.4% (95% CI 29.7, 35.1). The factors associated with a higher cumulative risk of false positive recall were: previous benign breast disease (OR = 8.48; CI 7.39, 9.73), perimenopausal status (OR = 1.62; CI 1.12, 2.34), body mass index above 27.3 (OR = 1.17; CI 1.02, 1.34), and age 50-54 years (OR = 1.15; CI 1.00, 1.31). CONCLUSIONS One third of women could have at least one false positive recall over 10 biennial screens. Women participating in screening programmes should be informed about this risk, especially those with associated factors.