Can a novel clinical risk score improve pneumonia prediction in acute stroke care? A UK multicenter cohort study

Abstract

Background: Pneumonia frequently complicates stroke and has amajor impact on outcome.Wederived and internally validated a simple clinical risk score for predicting stroke-associated pneumonia (SAP), and compared the performance with an existing score (A2DS2). Methods and Results--We extracted data for patients with ischemic stroke or intracerebral hemorrhage from the Sentinel Stroke National Audit Programme multicenter UK registry. The data were randomly allocated into derivation (n=11 551) and validation (n=11 648) samples. A multivariable logistic regression model was fitted to the derivation data to predict SAP in the first 7 days of admission. The characteristics of the score were evaluated using receiver operating characteristics (discrimination) and by plotting predicted versus observed SAPfrequency in deciles of risk (calibration). Prevalence ofSAPwas 6.7% overall. The final 22-point score (ISAN: prestroke Independence [modified Rankin scale], Sex, Age, National Institutes of Health Stroke Scale) exhibited good discrimination in the ischemic stroke derivation (C-statistic 0.79; 95% CI 0.77 to 0.81) and validation (C-statistic 0.78; 95% CI 0.76 to 0.80) samples. It was well calibrated in ischemic stroke andwas further classified intomeaningful risk groups (low0 to 5,medium6 to10, high 11 to 14, and very high =15) associated with SAP frequencies of 1.6%, 4.9%, 12.6%, and 26.4%, respectively, in the validation sample. Discrimination for both scores was similar, although they performed less well in the intracerebral hemorrhage patients with an apparent ceiling effect. Conclusions-The ISAN score is a simple tool for predicting SAP in clinical practice. External validation is required in ischemic and hemorrhagic stroke cohorts.