Disability as a covariate in risk adjustment models for predicting hospital deaths

Risk-adjusted hospital mortality rates are frequently used as putative indicators of hospital quality. These figures could become increasingly important as efforts escalate to contain U.S. health care costs while simultaneously maintaining or improving quality of care. Most risk adjustment methods today employ coded diagnostic information sometimes supplemented with more detailed clinical data obtained from medical records. This article considers whether risk-adjusted hospital mortality rates should account for baseline patient disability. Accounting for baseline disability when calculating hospital mortality rates makes clinical sense, especially for conditions such as heart failure or coronary artery bypass grafting surgery, where patients' cardiac-related functional status strongly predicts their imminent outcomes. A small body of research suggests the strength of disability in predicting hospital mortality, even in comparison with indicators of acute physiologic status and comorbid illness. However, the feasibility of obtaining complete and accurate data on patients' baseline disability will be challenging and requires further investigation. The risk of not adjusting for baseline disability could be efforts by physicians and hospitals to avoid treating patients with significant disabilities.