  Quality metrics in health care refer to a variety of measures used mainly to
characterize what should have been done for a patient or the health
consequences of what was done. When estimating quality of health care, often
many metrics are measured and then combined to provide an overall estimate
either at the patient level or at higher levels of accountability, such as the
provider organization, insurer, or even geographic area. Racial/ethnic
disparities are defined as the mean difference in overall quality between
minorities and Whites not justified by underlying health conditions or patient
preferences. However, several statistical features of health care quality data
have frequently been ignored: quality is a theoretical construct that is not
directly observed; the quality metrics are measured on different scales or, if
measured on the same scale, have different baseline rates; the structure of the
construct is likely multidimensional; and metrics are correlated
within-patients. We address these features and utilize multi-dimensional item
response theory models to estimate racial/ethnic quality disparities. Quality
metrics measured on 93,000 adults with schizophrenia residing in 5 U.S. states
illustrate approaches.
