A large literature establishes the presence of racial differences in healthcare using methods which assume that the covariates used for risk-adjustment affect whites and blacks equally. If incorrect, this assumption may overstate (or understate) the racial gap in treatment disparities.
We sought to determine whether models that allow for separate coefficients for whites and blacks (i.e. race-specific models) altered the measurement of racial disparities in treatments.
Design, Setting, and Participants
We used data from the Cardiovascular Cooperative Project, which has data on 130,709 white and 8,286 black patients admitted with an acute myocardial infarction during 1994 and 1995.
Main Outcome Measures
We examined rates of six treatments using two models: the conventional “common-effects” model which assumes that all covariates affect whites and black equally, and a race-specific model that allowed the effect of each covariate to vary by race.
Using the conventional common-effects models, we found that blacks were less likely to receive five of the six treatments (odds ratios 0.90 to 1.64). When we used race-specific models, we found nearly identical racial disparities in treatments (odds ratios 0.93 to 1.75) We were unable to identify any interaction effect which systematically suggested the presence of race specific effects.
The use race-specific models to perform risk-adjustment yields estimates of the racial disparity in treatment that are identical to those obtained from them conventionally used common-effect model. Racial disparities in care are not the artifact of mis-specified models.