Reliability, validity and responsiveness of the German Short Musculoskeletal Function Assessment Questionnaire in patients undergoing surgical or conservative inpatient treatment

Objective: The patient-based evaluation of outcome is gaining increased importance. The aim of the study was to demonstrate the reliability, validity and responsiveness of the German version of the Short Musculoskeletal Function Assessment Questionnaire (SMFA-D) in patients undergoing surgical or conservative treatment. Methods: Three hundred and thirty-two patients suffering from osteoarthritis of the hip or knee, rheumatoid arthritis or rotator cuff tear undergoing surgical or medical inpatient treatment were followed up for 12 month. Patients underwent both SMFA-D and other assessments and clinical as well as radiological examinations. Reliability, validity and responsiveness of the SMFA-D were evaluated. Results: Values of the SMFA-D subscales, Function index (M 22-49, SD 12-20, range 0-96) and Bother index (M 29-52, SD 15-23, range 0-100), showed a normal distribution. Internal consistency (0.88-0.97) and retest reliability (0.71-0.96) coefficients were satisfactory to excellent. In most cases, the SMFA-D correlated significantly with function tests, physicians' function ratings, patients' pain ratings and other quality-of-life questionnaires in all patient subgroups. The results support both the construct and criterion validity of the measure. Different patient groups and subgroups could be discriminated with the SMFA-D scales. The standardized response means of SMFA-D subscales were in surgical patients better than in conservatively treated patients and comparable to those of the SF-36 Physical Component Summary scale. Conclusions: The German version of SMFA is a reliable, valid and responsive questionnaire in patients with osteoarthritis of the hip or knee, rheumatoid arthritis or rotator cuff tear undergoing surgical or medical inpatient treatment. Thus, the use of the SMFA-D in these patients can be recommended.