Responsiveness and minimal clinically important difference of the Mini-BESTest in patients with Parkinson's disease

Background: Balance problems in Parkinson's Disease (PD) require appropriate evaluation. While the Mini-BESTest is commonly used to assess dynamic balance, some of its psychometric properties have not yet been addressed. Research question: What is the responsiveness and the Minimal Clinically Important Difference (MCID) of the Mini-BESTest in patients with PD? Methods: One-hundred forty-eight patients with PD underwent a treatment specific for balance skills (1-h session, three times/week for four weeks). All patients were initially evaluated with the Mini-BESTest and Activities-Specific Balance Confidence scale 5-levels (ABC-5L). Post-treatment, patients were assessed with the Mini-BESTest, ABC-5L and Global Rating of Change (GRC, both patient- and physiotherapist-rated). Responsiveness to treatment and MCID were calculated with distribution and anchor-based methods: effect size, area under the curve (AUC) of receiver operating characteristics (ROC), and correlations between evaluations (change in score of Mini-BESTest, ABC-5L, GRC). Eleven a priori hypotheses were formulated for testing responsiveness. Results: The effect size of treatment measured with the Mini-BESTest was 0.44, revealing moderate responsiveness. AUCs were 0.75, 0.82 and 0.59 for the patient-rated GRC, physiotherapist-rated GRC and ABC-5L, respectively. There was a moderate correlation between changes in the Mini-BESTest and patient-rated (r_s = 0.42) or physiotherapist-rated (r_s = 0.62) GRC scores. Conversely, a low correlation (r_s = 0.17) was found between changes in the Mini-BESTest and ABC-5L. Consequently, 72.7% of hypotheses were met. The Mini-BESTest MCID was between 3.4 and 4.0 when calculated with distribution and anchor-based methods, respectively. Significance: The Mini-BESTest showed moderate responsiveness for detecting treatment-related improvement in dynamic balance. A 4.0-point MCID value is useful to identify clinical effects of balance rehabilitation in a single patient with PD. Values ranging from 3.4 and 4.0 are recommended for interpretation of results at a group level.