COMPARATIVE RESPONSIVENESS OF GENERIC VERSUS DISEASE-SPECIFIC AND WEIGHTED VERSUS UNWEIGHTED HEALTH-STATUS MEASURES IN CARPAL-TUNNEL SYNDROME

OBJECTIVES. The authors evaluated the relative responsiveness to chang e of generic versus disease-specific and unweighted versus weighted he alth status measures in carpal tunnel syndrome (CTS). METHODS. Data we re obtained from 196 subjects followed in a prospective community-base d cohort study in Maine who underwent carpal tunnel release (The Maine Carpal Tunnel Syndrome Study). Patients were evaluated before and 6 m onths after surgery. The disease-specific, unweighted severity score w as derived from the validated Carpal Tunnel Syndrome Assessment Questi onnaire. Patients were asked to rate the importance of each symptom in cluded in the severity score. Each severity question was weighted by i ts importance, creating a disease-specific weighted score. Generic ins truments were the SF-36, SF-12, and a Quality of Life Rating Scale. Se nsitivity to change was calculated with the standardized response mean (SRM, mean change/standard deviation of change) as well as the effect size (ES, mean change/standard deviation of baseline values). The abi lity of the instruments to distinguish clinically important difference s was assessed by correlating the changes in scores with global rating s on satisfaction and perceived improvement as external criteria. RESU LTS. The disease-specific weighted score (SRM: 1.56, ES: 1.99) was mor e responsive than the unweighted score (SRM: 1.36, ES: 1.57). The Qual ity of Life Rating Scale, SF-36, and SF-12 subscales were less sensiti ve to change, with standardized response means and effect sizes that r anged from -0.23 to 0.88. The ability to distinguish clinically import ant differences was higher for the two disease-specific scales. The co efficients of correlation with the external criteria ranged from 0.50 to 0.56 for the unweighted score and 0.56 to 0.62 for the weighted sco re and were significantly stronger than the correlations between exter nal measures and the most responsive subscale of the SF-36 (Bodily Pai n subscale, r = 0.36). The SF-12 health survey performed as well as th e SF-36 in term of responsiveness and ability to distinguish clinicall y important change. CONCLUSIONS. Disease-specific measures were superi or to generic measures in capturing clinical change after carpal tunne l release, and a weighted score was slightly more responsive than the unweighted score. The SF-12 showed comparable psychometric properties compared with the longer 36-item Short-Form Survey.