Abstract P635: Polygenic Risk Scores Augment Stroke Subtyping and Outcome Evaluation

Objective: To determine whether Polygenic Risk Scores (PRS) derived from MEGASTROKE is associated with ischemic stroke (IS) and its subtypes in an independent tertiary healthcare system and to identify PRS derived from gene-sets of known biological pathways associated with IS and its outcomes (mortality and recurrent stroke). Methods: Controls(n=19806/7484, age≥69/79) and cases(n=1184/951 for discovery/replication) of acute IS with European ancestry and clinical risk factors identified by leveraging the Geisinger Electronic Health Record (EHR) and chart review confirmation. All Geisinger MyCode patients with age ≥69/79, without any stroke-related diagnostic codes as low-risk control. Genetic heritability and genetic correlation between Geisinger and MEGASTROKE(EUR) using the summary statistics of GWAS by LDSC. All PRS for any stroke — AS, any ischemic stroke — AIS, large artery stroke — LAS, cardioembolic stroke — CES, and small vessel stroke — SVS constructed by PRSice-2. PRS (top or bottom quantiles) derived from 7350 gene-sets of GO Biological Process was used to stratify the IS. Results: A moderate heritability (10-20%) for Geisinger sample as well as the genetic correlation between MEGASTROKE and the Geisinger cohort was identified. Gene sets analyses highlighted the association of PRS with Gene Ontology terms (vascular endothelial growth factor, amyloid precursor protein, and atherosclerosis). The PRS LAS , PRS CES , and PRS SVS explained the most variance of the corresponding subtypes of Geisinger IS suggesting shared etiologies and corroborated Geisinger TOAST subtyping. We further evaluate PRS derived from the gene-sets of which GO terms may best differentiate the survival in IS cases with the corresponding high or low genetic burden. The result from the Cox regression analysis showed simultaneously the effect of several risk factors including PRS on mortality and recurrent stroke probabilities. Conclusions: We provide the first evidence that PRSs derived from MEGASTROKE have value in identifying shared etiologies and determining stroke subtypes.