One question might be capable of replacing the Shoulder Pain and Disability Index (SPADI) when measuring disability: a prospective cohort study

Questions: Is it possible to replace the Shoulder Pain and Disability Index (SPADI) with a single substitute question for people with shoulder pain, when measuring disability and how well does this substitute question perform as a predictor for recovery. Design: A prospective cohort study. Participants: A total of 356 patients with shoulder pain in primary care. Analyses: Convergent, divergent, and “known” groups validity were assessed by using hypotheses testing. Responsiveness was assessed using the Receiver Operating Curve and hypothesis testing. In addition, we performed multivariate regression to assess if the substitute question showed similar properties as the SPADI and if it affected the model itself, using recovery as an outcome. Results: The Spearman correlation coefficient between the total SPADI score and the substitute question was high, and moderate with the Shoulder Disability Questionnaire. The correlation between the substitute question and the EQ-5D-3L was low and the responsiveness was acceptable. The substitute question did not significantly contribute to both prognostic prediction models as opposed to the SPADI. Regardless all models showed poor to fair discrimination. Conclusion: The single question is a reasonable substitute for the SPADI and can be used as a screening instrument for shoulder disability in primary clinical practice. It has slightly poorer predictive power and should therefore not be used for prognosis