A composite disease activity scale for clinical practice, observational studies, and clinical trials: the patient activity scale (PAS/PAS-II).

OBJECTIVE: To develop and validate a composite patient self-report disease activity scale for use in clinical practice and in observational studies and clinical trials.
METHODS: A total of 9078 patients with rheumatoid arthritis completed detailed questionnaires that included measure of quality of life in the form of utilities. We evaluated several disease activity scales by measuring their agreement with the utility scales, and also their assessed ability to predict mortality and prescription for anti-tumor necrosis factor therapy.
RESULTS: A composite index composed of a visual analog scale (VAS) for pain, a patient global VAS, and the Health Assessment Questionnaire (HAQ) or the HAQ II formed the Patient Activity Scale (PAS) and PAS-II. These scales performed as well as or better than longer, more complex scales.
CONCLUSION: A simple, useful clinical scale, the PAS or PAS-II, can be formed by the use of common clinical variables. It is well correlated with and relevant to a wide range of clinical variables. This scale should be useful for comparative studies, clinical care, and regulatory documentation.