Eighteen years of mammography experience in an HMO: 1975-1992

Abstract

Objective: To describe the mammographic experience for the years 1975 to 1992 at Kaiser Permanente, Northwest Region (KPNW).

Setting: Large, group practices HMO.

Design: Clinical databases.

Participants: KPNW women in various subgroups.

Main outcome measures: Mammogram rates.

Results: The rate of mammography at KPNW was fairly low (2% to 5%) until 1983, when it began to rise rapidly, almost exclusively as a result of a great increase in screening examinations of otherwise normal women. By 1992 the annual rate of mammography had increased to 40.2% for all women over age 40, and 52.4% for women aged 50 to 69. Women aged 40 to 49 and those over 70 had rates 10% to 15% lower than women aged 50 to 69. Summary figures for all KPNW women hide the striking effect of duration of membership in this HMO. Women aged 50 to 69 who had been members for at least 2 years had mammography rates (at least one examination in that 2-year period) of 75% to 76%. Longer membership resulted in gradually higher rates. The annual mammogram rate for women with 4 years of membership was 58%.

Conclusions: Though there may be significant personal barriers to regular mammography, the effect may be less important in the HMO setting. An efficient, organized system can effect high rates of mammographic screening. The longer a woman remains a member of such an organization the greater her likelihood of receiving regular screening mammograms.