Abstract WP184: Identifying Optimal Cut Points Of National Institutes Of Health Stroke Scale To Predict Mortality: A Population-based Assessment

Background: Ischemic stroke is the 5 th leading cause of death in the US. As a measure of stroke severity, initial NIHSS has been used to predict clinical outcome. We sought to identify the optimal cut-points of NIHSS at initial presentation that are associated with higher 30-day mortality. Methods: In 2005, 2010, and 2015 all hospitalized, first acute ischemic stroke events occurring within the Greater Cincinnati area were ascertained. Potential ischemic stroke cases underwent chart abstraction and physician adjudication, including retrospective NIHSS score (range 0 - 42) based on clinical findings at initial presentation. Descriptive statistics for NIHSS were estimated by study year, demographics, and medical history. Data regarding mortality was obtained from the National Death Index. The Contal and O’Quigley method based on a modified log-rank test statistic was used to determine cut-points of the NIHSS score associated with 30-day mortality, and hazard ratios were obtained from Cox models with adjustment for sex, race, and age. Results: In 2005, 2010, and 2015 there were 1704, 1818 and 1852 ischemic stroke events with 30-day mortality rates of 10.5%, 9.6% and 9.0%, respectively. Optimal cut-points of NIHSS <9, 9-16 and >16 were identified. Across all 3 periods, 3431 (84.5%) cases had NIHSS 0-8, 352 (8.7%) had NIHSS 9-16 and 274 (6.8%) >16. Kaplan Meier Survival Curves for the 3 NIHSS groups are shown in the Figure. Strokes with NIHSS >16 at initial presentation were associated with a 15-fold (HR with 95% CI: 13, 19) increase in the risk of death at 30-days compared to those with NIHSS <9. Discussion: NIH Stroke Scale scores are a reliable predictor of mortality, with higher NIHSS scores having higher risk of death. The cut points reported identify subgroups of stroke patients with dramatically different prognoses. Future studies should assess if this excess mortality risk among severe strokes persists after the more widespread implementation of thrombectomy beyond 2015.