Determining the minimal important change in patient reported outcomes for carpal tunnel syndrome

BACKGROUND: Patient reported outcome measures (PROMs) can be used to quantify responses to treatment and for quality measurement purposes. However, the clinical importance of a given change in a PROM score is hard to interpret. The minimal important change (MIC) is the smallest change in score that patients consider important. OBJECTIVE: To estimate MICs for three PROMs at 3- and 9-month follow-ups for a large five-institution sample of patients with carpal tunnel syndrome. DESIGN: Cohort study. SETTING: Two university, two Veterans Affairs, and one community nonprofit health care systems. PATIENTS: Patients receiving initial consultation with a hand surgeon for carpal tunnel syndrome. MEASURES AND METHODS: Patients completed baseline, 3-month, and 9-month PROMs: the Boston Carpal Tunnel Questionnaire Symptom (BCTQ-SS) and Functioning (BCTQ-FN) Scales, and the Quick Disabilities of the Arm, Shoulder, and Hand (QDASH) scale. Anchor-based methods and Youden J-statistics were used to find the optimal MIC cut points that maximized sensitivity and specificity for patients being satisfied with the outcome of treatment. RESULTS: Six hundred thirty-five patients completed the baseline PROMs, and 551 (87%) and 516 (81%) completed the 3- and 9-month PROMs, respectively. The percentage of patients who were at least somewhat satisfied with the results of treatment differed between the carpal tunnel release and nonoperative subgroups (91% vs. 67% at 9 months), as did the MIC estimates. At 9 months, 295 of 326 (91%) of carpal tunnel release patients were satisfied with the results of treatment, with MICs of 0.81, 0.66, and 15.7 for the BCTQ-SS, BCTQ-FN, and QDASH, respectively. We also produced MICs for the 3-month assessment, the nonoperative, and overall samples. CONCLUSIONS: These MIC estimates can be used in clinics or research to gauge response to treatment and used in the design of PROM-based quality measures.