Abstract MP56: A Gene-centric Association Study of Activated Partial Thromoplastin Time in European Americans and African Americans: The ARIC Study

Abstract

Introduction: Activated partial thromboplastin time (aPTT) is commonly used to screen for coagulation factor deficiencies. Shorter aPTT is also a risk marker for incident and recurrent venous thromboembolism (VTE). Genetic factors influencing aPTT are not well understood. aPTT was associated with common genetic variants of coagulation factors V (F5), XI (F11), XII (F12), KNG1, HRG, and ABO in previously reported genome-wide association studies (GWAS) that were conducted in individuals of European ancestry; no data have been reported in other race groups. Hypothesis: The present study aimed to identify aPTT-related gene variants in European Americans (EAs) and African Americans (AAs). Methods: We conducted a large-scale candidate gene study for aPTT in 9,719 EAs and 2,799 AAs from the Atherosclerosis Risk in Communities (ARIC) study. Subjects on anticoagulants were excluded. Nearly 50,000 single nucleotide polymorphisms (SNPs) located in 2,100 candidate genes were genotyped by the Candidate gene Association Resource (CARe) gene chip. The association between each SNP and aPTT was assessed with an additive genetic model using linear regression adjusted for age, sex, and field center. We additionally adjusted for principal components in AAs to account for potential population stratification. P-value for significant threshold was set at 2x10-6 after accounting for multiple testing. Results: In EAs, fifty-five SNPs from F5, HRG, KNG1, F11, F12, and ABO genes exceeded the significant p-value threshold. The signals in HRG, KNG1, F11, F12, and ABO genes replicated the previously reported GWAS findings. The top variant in F5 identified in EAs was only weakly associated with the previously reported GWAS variant (rs2239852, p=1.89x10-08 and r2=0.02 with rs9332701 reported in the previously reported GWAS). In AAs, twenty-seven SNPs from the HRG, KNG1, F12, and ABO genes were significantly associated with aPTT. The top signals from the HRG (rs9898, p=1.19x10-27) and KNG1 genes ( rs710446 , p=8.41x10-42) replicated the previously reported signals in EAs with similar effect size and direction of association, but the top signals in the F12 and ABO genes were weakly associated with the previously reported variants in EAs (rs1801020 in F12: p=1.01x10-84 and r2=0.12 with rs2545801, and rs8176722 in ABO: p=1.62x10-29 and r2=0.26 with rs687621 , respectively). Conclusions: Our study replicated the previously reported associations of aPTT with HRG, KNG1, F11, F12, and ABO genes in EAs and with HRG and KNG1 in AAs. The signals from F5 identified in EAs and from F12 and ABO identified in AAs may represent new genetic variants for aPTT.