Minimal clinically important difference for the Boston Carpal Tunnel Questionnaire: new insights and review of literature.

No consensus exists about the minimal clinically important difference for the Boston Carpal Tunnel Questionnaire, which hampers its clinical application. This study assessed the minimal clinically important difference of this questionnaire. The Boston Carpal Tunnel Questionnaire was completed by 180 patients, with clinically defined carpal tunnel syndrome, preoperatively and at about 8 months follow-up after carpal tunnel release, together with a six-point scale for perceived improvement. Receiver operator characteristics curves showed that relative changes in Symptom Severity Scale and Functional Status Scale scores correspond better to a clinically relevant improvement than absolute changes. The minimal clinically important difference should be individually calculated from baseline Symptom Severity Scale and Functional Status Scale scores, as patients experiencing more symptoms require more improvement to notice a clinically important difference. By taking this into account, the Boston Carpal Tunnel Questionnaire is more meaningful as an outcome measure in research and clinical practice.