Comparison of Hospital Performance in Acute Ischemic Stroke Based on Mortality and Functional Outcome in South Korea

Abstract

Background: Recent evidence suggests a correlation between modified Rankin Scale-based measures, an outcome measure commonly used in acute stroke trials, and mortality-based measures used by health agencies in the evaluation of hospital performance. We aimed to examine whether the 2 types of measures are interchangeable in relation to evaluation of hospital performance in acute ischemic stroke.

Methods: Five outcome measures, unfavorable functional outcome (3-month modified Rankin Scale score ≥2), death or dependency (3-month modified Rankin Scale score ≥3), 1-month mortality, 3-month mortality, and 1-year mortality, were collected for 8292 individuals who were hospitalized for acute ischemic stroke between January 2014 and May 2015 in 14 hospitals participating in the Clinical Research Collaboration for Stroke in Korea - National Institute of Health registry. Hierarchical regression models were used to calculate per-hospital risk-adjusted outcome rates for each measure. Hospitals were ranked and grouped based on the risk-adjusted outcome rates, and the correlations between the modified Rankin Scale-based and mortality-based ranking and their intermeasure reliability in categorizing hospital performance were analyzed.

Results: The comparison between the ranking based on the unfavorable functional outcome and that based on 1-year mortality resulted in a Spearman correlation coefficient of -0.29 and Kendall rank coefficient of -0.23, and the comparison of grouping based on these 2 types of ranks resulted in a weighted kappa of 0.123 for the grouping in the top 33%/middle 33%/bottom 33% and 0.25 for the grouping in the top 20%/middle 60%/bottom 20%, respectively. No significant correlation or similarity in grouping capacities were found between the rankings based on the functional outcome measures and those based on the mortality measures.

Conclusions: This study shows that regardless of clinical correlation at an individual patient level, functional outcome-based measures and mortality-based measures are not interchangeable in the evaluation of hospital performance in acute ischemic stroke.