Estimating the Minimal Clinically Important Difference on the Visual Analogue Scale for Carpometacarpal Thumb Joint Osteoarthritis.

Background: The minimal clinically important difference (MCID) is the smallest perceived treatment effect that patients deem clinically significant. There is currently no agreement on an appropriate MCID for the pain visual analogue scale (VAS) in the context of thumb osteoarthritis (OA).

Methods: We approximated MCIDs using a distribution-based approach that pooled standard deviations (SDs) associated with baseline mean values of the pain VAS (0-100 mm). We extracted the data from randomized controlled trials (RCTs) included in a systematic review of adults with long-term OA of the thumb. We excluded RCTs that did not report baseline SD values. The MCIDs were derived at 0.4 and 0.5 SDs of the pooled SD and compared with previously published MCIDs for the pain VAS in OA.

Results: A total of 403 patients were pooled from 7 RCTs for the analysis. The mean baseline VAS pain score was 5.6 cm. We derived an MCID of 0.72 cm at 0.4 SDs and 0.91 cm at 0.5 SDs using baseline SDs. We found that MCIDs derived from a distribution-based approach approximated published MCIDs for the VAS for pain for OA in the knee and hip.

Conclusion: The authors propose that a change of 0.7 to 0.9 cm on the VAS is clinically meaningful in the context of long-term OA of the thumb.