Establishing the Minimal Clinical Important Difference and Minimal Detectable Change for the Cumberland Ankle Instability Tool.

Objective: To establish the minimal detectable change (MDC) and minimal clinically important difference (MCID) for the Cumberland Ankle Instability Tool (CAIT) in a population with chronic ankle instability (CAI).

Design: Experimental cohort.

Setting: Laboratory.

Participants: A convenience sample of individuals with CAI (N=50; 12 men; 38 women; episodes of giving way, 5.84±12.54mo). CAI inclusion criteria included a history of an ankle sprain, recurrent episodes of giving way, and a CAIT score ≤25.

Interventions: Participants completed demographic information, an injury history questionnaire, and the CAIT. Participants then either participated in 4 weeks of wobble board balance training, resistance tubing strength training, or no intervention. After 4 weeks, participants recompleted the CAIT and recorded their global rating of change (GRC).

Main Outcome Measures: Dependent variables were pre- and postintervention scores on the CAIT and postintervention GRC. The MDC with 95% confidence interval was calculated. A receiver operating characteristic (ROC) curve identified the optimal CAIT cut point (MCID) between improved and unimproved individuals on the basis of their GRC. The area under the curve was used to identify a significant ROC curve (α=.05).

Results: The average CAIT score preintervention was 16.8±5.6, and postintervention, it was 20.0±5.2. Thirty-one participants (62%) rated themselves as improved on the GRC scale, whereas 19 (38%) were not improved. The ROC curve was significant (area under the curve, .797; P=.001), indicating that the CAIT change score significantly predicted clinical status. The MDC was 3.08, and the MCID was ≥3 points.

Conclusions: The CAIT has an MDC and MCID of ≥3 points. When CAIT scores are used to assess patient change over time, these scores should be used as a minimum threshold to indicate detectable and clinically meaningful improvement.