Development and psychometric evaluation of the PMR-Impact Scale: a new patient reported outcome measure for polymyalgia rheumatica.

The PMR-IS offers researchers a new way to assess patient-reported outcomes in clinical studies of PMR. It has been developed robustly, with patient input at every stage. It has good construct validity and test re-test reliability. Further work is needed to fully establish its responsiveness and interpretability parameters and assess its real-world clinical utility.