Abstract W P328: Comparative Analysis of Two Methods to Score the modified Rankin Scale: Rankin Focused Assessment and Simple modified Rankin Scale Questionnaire

Abstract

Background: The modified Rankin Scale (mRS) of global disability is the most common primary endpoint in acute stroke clinical trials. Since intuitive scoring of the mRS yields only modest inter-rater reliability, more formal scoring methods, with improved reliability, have recently been developed, but little compared. Methods: The Rankin Focused Assessment (RFA) is a formally operationalized, rater-scoring method using all available data, including patient and caretaker reports, medical records, and direct patient exam. The simple modified Rankin Scale questionnaire is a formally operationalized, patient report-based scoring method. We obtained 3 month mRS scores using the RFA and smRSq in consecutive patients enrolled in the NIH FAST-MAG trial. Results: Among 143 patients assessed at 3 months, the mean age was 66.9 (range 40-89+), 48.2% were female, and stroke subtype was ischemic in 70.6%. Amongst living patients, 3-month assessments were performed in person in 95% and by phone in 5%. With the RFA, mean mRS score was 2.2 and with the smRSq 2.1. The two instruments showed high general rates of agreement amongst all patients: raw percent agreement was 117/143 (84.0%), weighted kappa 0.92 (95% CI 0.89-0.95) and unweighted kappa 0.82 (95% CI 0.75-0.88). Agreement was modestly higher for in person than for phone visits (weighted kappa 0.93 vs 0.77). Of the 26 discrepancies in scoring, 18 (69%) had higher and 8 (31%) lower disability scores with the RFA than with the smRSq. Content analysis of discrepant scores indicated the RFA had greater sensitivity to aspects of disability under-captured by patient self-report. Conclusion: The RFA and the smRSq show excellent convergent validity as tools to score the modified Rankin Scale. The findings of this study suggest that both are useful and have distinct advantages: the smRSq has greater ease of administration due to its brevity and the RFA has greater clinical validity with sensitivity to all sources of disability.