A patient-specific measure of change in maximal function.

We designed a short, patient-specific index that measures changes in maximal physical, mental, and emotional function. A baseline component, given at the initial interview, documents the patients' usual activities that require the most physical exertion and mental effort, as well as the patients' ability to cope with stress. A transition component assesses the subsequent change from these patient-specific norms. The index was evaluated in two separate studies involving medical and surgical patients. In the first study, the index was administered twice to 40 patients. Reliability was excellent for all three aspects of function. The transition index had a high degree of internal consistency. In a second study of 43 hospitalized patients, the validity of the index was assessed by comparing its performance with the Sickness Impact Profile; high correlations were found. In addition, the overall patterns of change differed in the expected directions in the medical and surgical groups. This index is unique in its ability to measure change directly, is interpretable in individual patients, and could be easily applied in clinical practice and research.