Concordance of population-based estimates of mammography screening

Estimates of adherence to mammography screening guidelines vary, in part, due to lack of consensus on defining adherence. This study estimated adherence to repeat (two successive on-time screenings) and regular screening (three or more successive screenings) and evaluated the impact of varying operational definitions and evaluation periods.

The study included women aged 50-80 without a history of breast cancer who: were on a biennial screening cycle and due for a screening mammogram between 1995 and 1996; underwent screening (index date) in response to a reminder letter; and belonged to Group Health, an integrated health care delivery system in Washington State, for 6 or more years after the index date. Automated records provided information on enrollment, health care utilization, and procedures.

Among 1336 women, 67-82% experienced a repeat screen. Adherence to regular screening over the 6-year evaluation period was 42-84%--and higher with longer allowable intervals between screenings, when definitions did not require on-schedule screenings, when intervals were reset after a diagnostic mammogram, and for shorter evaluation periods.

Estimates of adherence to screening guidelines varied by the operational definition of "success" and time period of evaluation. Consensus in definitions and terminology is needed to compare evaluations.