Mammography screening rates decline: A person-time approach to evaluation

Objectives Early detection through mammography can reduce breast cancer mortality. This cohort study evaluated trends in mammography screening, demonstrating a person-time approach. Methods Included were women HMO members aged 50–69 from 1999 to 2002 who had not had breast cancer, dysplasia, fibrocystic disease, or implant. The amount of person-time covered by mammography as a percent of the time eligible for mammography screening (the prevention index (PI)) was calculated using electronic data. The denominator was the time during which the guidelines recommended that each participant should have been covered by a mammogram (every 24 months), excluding times when breast mass, abnormal mammogram, galactorrhea, or other breast disorders were under evaluation. The numerator was the time during which she was covered by a mammogram. Results The number of women who contributed person-time increased from 43,283 to 49,512 and the number of screening mammograms declined from 23,586 to 22,719. The overall PI for screening mammography declined from 67.0 (67% of eligible person-time was appropriately covered by a mammogram) to 62.5, and the proportion of women with no coverage during a given year increased 16%. Conclusions This study shows a declining pattern of mammography screening using a person-time approach, a decline greater than that shown by methods that include diagnostic mammograms. The study highlights opportunities for use of the PI and quality improvement initiatives to improve breast cancer outcomes.