Background: Medicare data may be a useful source for determining the utilization of mammography among elderly women, but the accuracy of these data has not been established.
Objective: We determined whether Medicare physician billing claims are an accurate reflection of mammography utilization among women ages 65 and older and whether they can be used to assess the use of screening as compared with diagnostic mammography.
Data sources: Mammography use was assessed using Medicare billing claims and radiology reports from 2 mammography registries; the San Francisco Mammography Registry and the New Mexico Mammography Registry.
Methods: Completeness of the Medicare data was assessed by comparing mammography use based on Medicare, with radiology reports from the mammography registries, which served as the referent standard. Capture rates for Medicare claims for individual mammograms were examined, and women were characterized as having undergone at least 1 mammogram within each 2-year period based on the Medicare data, and these rates were compared with the referent standard. To determine whether Medicare data can distinguish between screening and diagnostic mammography, we performed a classification analysis using the mammography registries screening/diagnostic designation as the referent standard (dependent variable) and Medicare claim information as the independent/predictor variable. On the basis of the mammogram level classification analysis, women were categorized as having been frequently screened (at least 2 screening mammograms spaced by 12 to 36 months), screened (at least 1 screening mammogram), or not screened.
Subjects: Women ages 65 and older, diagnosed with breast cancer between 1992-1999, who had at least 1 mammogram between 1992-1999 were examined.
Results: A total of 3340 mammograms were obtained in 1371 women between 1992 and 1999. Overall, 83% of mammograms obtained by these women had a corresponding billing claim in Medicare. This increased from 65% in 1992 to 90% in 1999. Of women who underwent at least 1 mammogram during each 2-year period per the referent standard, 94% of women were accurately classified by Medicare claims as also having undergone mammography during the same 2-year period. In multivariable analysis, a mammogram was more likely to be associated with a billing claim over time, for women 80 years or older, and for white and Asian as compared with Hispanic women. Neither socioeconomic status nor screening/diagnostic designation affected the likelihood that a mammogram would be associated with a billing claim. The Medicare data accurately categorized a given mammogram as screening or diagnostic for 87.5% of mammograms. Lastly, there was moderate to substantial agreement in the categorization of women as frequently screened, screened or not screened between the 2 data sets (weighted kappa 0.74, 95% confidence interval 0.70-0.78).
Conclusion: Medicare administrative claims are reliable for assessment of mammography utilization and have become more accurate over time. Medicare claims data also provide a mechanism for designating mammography as screening or diagnostic, which subsequently may allow accurate description of a woman's screening history.