Platelet glycoprotein Ibα Kozak polymorphism is associated with an increased risk of ischemic stroke

Platelets are pivotal to the process of arterial thrombosis resulting in ischemic stroke. Occlusive thrombosis is initiated by the interaction of von Willebrand factor (vWf) and platelet glycoprotein (GP) Ib alpha. Three polymorphisms have been de scribed in GP Ib alpha (Kozak TIC polymorphism, variable number of tandem repeats [VMTR], and the human platelet antigen 2a [HPA-2a] [Thr] or HPA-2b [Met] at position 145), each of which may enhance the vWf and GP Ib alpha Interaction. This study investigated whether these polymorphisms are candidate genes for first-ever ischemic stroke. A hospital-based case-control study was conducted of 219 cases of first-ever ischemic stroke and 205 community controls randomly selected from the electoral roll and stratified by age, sex, and postal code. The subtypes of stroke were classified, the prevalence of conventional risk factors was recorded, and blood was collected to perform genotyping analysis for Kozak C or T alleles, VNTR, and HPA-2a/b. It was found that the Kozak TIC genotype was over-represented in the stroke group (32.2%) compared with controls (22.8%) (odds ratio [OR], 1.6; 95% confidence interval [Cr], 1.03-2.54; P < .03), and the association was still present even after adjusting for conventional risk factors. There was a trend in the increased prevalence of HPA-2a/b in stroke patients (15%) compared with controls (9.9%) (adjusted OR, 1.8; 95% Cl, 0.94-3.4; P = .07). No associations were seen with the VMTR polymorphism or with any of the polymorphisms with stroke subtype, It was concluded that the Kozak T/C polymorphism; which is associated with an increase in platelet GP Ib alpha surface expression, is an independent riskfactorfor first-ever ischemic stroke. (C) 2001 by The American Society of Hematology.