Methods for using Medicare data to compare procedure rates among Asians, blacks, Hispanics, Native Americans, and whites.

OBJECTIVE: Small sample sizes in Asian, Hispanic, and Native American groups and misreporting of race/ethnicity across all groups (including blacks and whites) limit the usefulness of racial/ethnic comparisons based on Medicare data. The objective of this paper is to compare procedure rates for these groups using Medicare data, to assess how small sample size and misreporting affect the validity of comparisons, and to compare rates after correcting for misreporting.

DATA: We use 1997 physician claims data for a 5 percent sample of Medicare beneficiaries aged 65 and older to study cardiac procedures and tests.

STUDY DESIGN: We calculate age and sex-adjusted rates and confidence intervals by race/ethnicity. Confidence intervals are compared among the groups. Out-of-sample data on misreporting of race/ethnicity are used to assess potential bias due to misreporting, and to correct for the bias.

PRINCIPAL FINDINGS: Sample sizes are sufficient to find significant ethnic and racial differences for most procedures studied. Blacks' rates tend to be lower than whites. Asian and Hispanic rates also tend to be lower than whites', and about the same as blacks'. Sample sizes for Native Americans are very small (about .1 percent of the data); nonetheless, some significant differences from whites can still be identified. Biases in rates due to misreporting are small (less than 10 percent) for blacks, Hispanics, and whites. Biases in rates for Asians and Native Americans are greater, and exceed 20 percent for some procedures.

CONCLUSIONS: Sample sizes for Asians, blacks, and Hispanics are generally adequate to permit meaningful comparisons with whites. Implementing a correction for misreporting makes Medicare data useful for all ethnic groups. Misreporting race/ethnicity and small sample sizes do not materially limit the usefulness of Medicare data for comparing rates among racial and ethnic groups.