Reliability, validity and responsiveness of the short musculoskeletal function assessment questionnaire (SMFA-D) in surgical patients with rheumatoid arthritis

Patient-centered outcome research has become more important in recent years. The German version of the Short Musculoskeletal Function Assessment Questionnaire (SMFA-D) provides good results in cases of trauma and osteoarthritis. Until today, no data for poly-articular and inflammatory diseases are available. This prospective clinical trial evaluates reliability, validity and responsiveness in patients with rheumatoid arthritis undergoing an operation. Respondents included 55 patients (48 women, 7 men, average age 60 years, ranging from 31 to 85 years) suffering from rheumatoid arthritis of the upper and lower limbs. Each patient answered a questionnaire 7 - 10 days before, on the preceding day, and 3 and 12 months after the operation. Patients underwent clinical and radiological examinations. Reliability, validity (criteria, construct, and discrimination) and responsiveness were evaluated. Good results could be found for reliability (function-index [FI] ICC = 0.94 - impairment-index [II] ICC = 0.94) and internal consistence (alpha = 0.90 to 0.96). Construct validity (FFb-H FI r= 0.81, BI r = 0.72, HAQ FI r = 0.86, BI r = 0.67, SF-36 FI r = 0.35, BI r = 0.87) and criterion validity (loss of function FI r = 0.54; BI r = 0.47; pain FI r = 0.55; BI r = 0.59) could be shown. Patients with and without crutches could be differentiated (discriminative validity). The responsiveness 12 months after operation was FI 0.24 and BI 0.34. No responsiveness was found for HAQ and FFb-H. The Short Musculoskeletal Function Assessment Questionnaire (SMFA-D) provides good results for reliability, validity and responsiveness in patients with rheumatoid arthritis. The results were better than in other assessment scores.