Reliability of the Modified Rankin Scale

BACKGROUND AND PURPOSE: A perceived weakness of the modified Rankin Scale is potential for interobserver variability. We undertook a systematic review of modified Rankin Scale reliability studies. METHODS: Two researchers independently reviewed the literature. Crossdisciplinary electronic databases were interrogated using the following key words: Stroke*; Cerebrovasc*; Modified Rankin*; Rankin Scale*; Oxford Handicap*; Observer variation*. Data were extracted according to prespecified criteria with decisions on inclusion by consensus. RESULTS: From 3461 titles, 10 studies (587 patients) were included. Reliability of modified Rankin Scale varied from weighted kappa=0.95 to kappa=0.25. Overall reliability of mRS was kappa=0.46; weighted kappa=0.90 (traditional modified Rankin Scale) and kappa=0.62; weighted kappa=0.87 (structured interview). CONCLUSION: There remains uncertainty regarding modified Rankin Scale reliability. Interobserver studies closest in design to large-scale clinical trials demonstrate potentially significant interobserver variability.