SPADI and QUICKDASH are similarly responsive in patients undergoing physical therapy for shoulder pain

Study Design: Prospective multicenter longitudinal cohort study. 
Background: A key component of assessing clinical effectiveness is to compare instruments measuring similar outcomes and to select one that is sufficiently responsive. Despite their widespread use in reporting outcome, the responsiveness of the SPADI and QuickDASH, have not been compared and reported within the same population.Objective: To compare the responsiveness of the Shoulder Pain and Disability Index (SPADI) and Quick Disabilities of the Arm, Shoulder and Hand (QuickDASH) in a single large cohort of patients. 
Methods: 767 patients referred to physical therapy with shoulder pain completed SPADI and QuickDASH questionnaires at baseline, six weeks and six months. Improvers and Non-Improvers were defined using a seven-point Global Rating of Change scale. Internal and external responsiveness was evaluated. 
Results: For Improvers, the effect size (ES) and standardized response mean (SRM) were large (>1.00) at six weeks for both the SPADI and QuickDASH and further increased for both measures at six months. For participants who worsened, negative ES and SRMs were larger at six weeks than six months. The area under the curve (AUC) was similar for both SPADI (0.81) and QuickDASH (0.78) increasing to 0.85 for both at six months. 
Conclusion: Both instruments are similarly able to discriminate between Clinical Improvers and Non-Improvers at either follow-up point.