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Purpose: To determine minimally clinically important difference (MCID) after carpal tunnel release in diabetic and non-diabetic patients using a patient-rated outcomes questionnaire, the Boston Carpal Tunnel Questionnaire (BCTQ).

Methods: We prospectively evaluated 114 patients (87 non-diabetic, 27 diabetic) undergoing carpal tunnel release. In addition to standard history and physical examination, we obtained preoperative electrodiagnostic studies to confirm Carpal Tunnel Syndrome (CTS). The BCTQ was administered before and after the surgery at 3 and 6 months. Patients were asked about their level of satisfaction at the final follow-up period. We applied the receiver operating characteristic (ROC) curve to determine the MCID of symptom and function severity scales of the questionnaire. Patient satisfaction rating was used as the reference standard to compare against the standardized change in scores after surgery for the 2 groups.

Results: For both diabetic and non-diabetic patients, symptom and function severity scales showed large effect size of >0.8 at 3 and 6 months after the surgery. At 6 months after surgery to be satisfied, diabetic patients required an MCID of 1.55 points for symptom scale and 2.05 points for function scale, whereas non-diabetic patients required 1.45 and 1.6 points, respectively (p<0.05).

Conclusion: Diabetic patients needed a greater improvement in BCTQ score to be satisfied on functional and symptom severity scales than non-diabetic patients. However, both groups had the same beneficial outcome after carpal tunnel release.