Improving the Reliability of Stroke Disability Grading in Clinical Trials and Clinical Practice

BACKGROUND AND PURPOSE: The modified Rankin Scale rates global disability after stroke and is the most comprehensive and widely used primary outcome measure in acute stroke trials. However, substantial interobserver variability in modified Rankin Scale scoring has been reported. This study sought to develop and validate a short, practicable structured assessment that would enhance interrater reliability. METHODS: The Rankin Focused Assessment was developed by selecting and refining elements from prior instruments. The Rankin Focused Assessment takes 3 to 5 minutes to apply and provides clear, operationalized criteria to distinguish the 7 assignable global disability levels. The Rankin Focused Assessment was prospectively validated 3 months poststroke among 50 consecutive patients enrolled in the Phase 3 National Institutes of Health Field Administration of Stroke Therapy-Magnesium (FAST-MAG) Trial. RESULTS: Among the 50 patients, mean age was 71.5 years (range, 43 to 93 years), 48% were female, and stroke subtype was hemorrhagic in 24%. At Day 90, 43 patients were alive and 7 had died. The modified Rankin Scale median was 2.0 and mean was 2.8. When pairs of 14 raters assessed all enrolled patients, the percent agreement was 94%, the weighted kappa was 0.99 (95% CI, 0.99 to 1.0), and the unweighted kappa was 0.93 (95% CI, 0.85 to 1.00). Among the 43 surviving patients, the percent agreement was 93%, the weighted kappa was 0.99 (0.98 to 1.0), and the unweighted kappa was 0.91 (0.82 to 1.00). CONCLUSIONS: The Rankin Focused Assessment yields high interrater reliability in the grading of final global disability among consecutive patients with stroke participating in a randomized clinical trial. The Rankin Focused Assessment is brief and practical for use in multicenter clinical trials and quality improvement activities.