Derivation of minimal clinically important difference score for the WHODAS 2.0 in mild traumatic brain injury

BACKGROUND: Mild traumatic brain injury (mTBI) treatment research is hindered by lack of clinically meaningful and responsive outcome measures. One promising measure is the World Health Organisation Disability Assessment Schedule 2.0 (WHODAS 2.0), although minimal clinically important differences (MCID) for have not been established. OBJECTIVE: To estimate MCID for the WHODAS 2.0 for mTBI. METHODS: We analysed two prospectively collected mTBI datasets (n = 225) attending adult outpatient clinics in British Columbia, Canada. Participants completed the 12-item WHODAS 2.0, Patient Global Impression of Change scale, and Rivermead Post-Concussion Symptoms Questionnaire. We used anchor- and distribution-based methods to explore MCIDs in WHODAS 2.0 scores. RESULTS: For Study 1 (n = 131), the anchor and distribution-based approaches produced minimal change estimates ranging from 1.3 to 2.8 interval scores. For Study 2 (n = 94), the anchor and distribution-based approaches produced minimal change estimates from 2.2 to 3.2 interval scores. For certain subgroups based on age, sex, and post-concussion severity, minimal change estimates were slightly higher. CONCLUSION: An MCID of 3.5 interval WHODAS 2.0 points would conservatively capture meaningful change in adults of varying age, sex, and post-concussion symptom severity. Such a uniform metric will assist future mTBI intervention studies to improve standards of care and evaluation of outcomes.