SHORT REPORT Glycoprotein Ib polymorphisms influence platelet plug formation under high shear rates Petra Jilma-Stohlawetz, 2 Monika Homoncik, 1 Bernd Jilma, 1 Maarten Knechtelsdorfer, 1 Petra Unger, 3 Christine Mannhalter, 3 Sentot Santoso 4 and Simon Panzer 2 1 Department of Clinical Pharmacology-TARGET, 2 Department of Blood Group Serology and Transfusion Medicine, 3 Clinical Institute of Medical and Chemical Laboratory Diagnostics, Vienna University, Austria, and 4 Institute for Clinical Immunology and Transfusion Medicine, Giessen, Germany Received 10 July 2002; accepted for publication 22 August 2002 Summary. Platelet polymorphisms (Kozak, VNTR and HPA-2) within glycoprotein (GP)Iba may be associated with an increased risk of arterial thrombosis. However, the functional role of these polymorphisms has not been clar- ified. Their influence on platelet plug formation under high shear rates was, therefore, examined in 233 healthy indi- viduals. Collagen–adrenaline-induced closure time was shorter in carriers of the C/D versus C/C VNTR allele and in homozygotes with the ()5)T/T versus ()5)C/T Kozak genotype as determined by novel polymerase chain reaction methods. The HPA-2 genotype had no effects, and the density of GPIba molecules was not influenced by GPIba genotypes. Keywords: GPIb, polymorphism, von Willebrand factor, platelet function, PFA-100. The glycoprotein (Gp) Ib/IX complex is the major receptor for von Willebrand factor (VWF), which mediates shear- stress-induced platelet adhesion and activation. Three genetically inherited polymorphisms of GpIba may affect its receptor function: a length polymorphism that results from a variable number of tandem repeats (VNTR) in the macroglycopeptide region of GpIba; the ()5)C/T dimorph- ism in the Kozak region; and, third, a 524C/T dimorphism, leading to the HPA-2 antigens, which may elicit allo- immune response. Controversial data have been published about an associ- ation of these polymorphisms with coronary artery disease (CAD) or cerebrovascular disease (CVD). While one case– control study found an association of the Kozak C/T dimorphism and CVD (Baker et al, 2001), other studies could not link the Kozak genotypes to CVD or CAD (Corral et al, 2000; Croft et al, 2000; Ishida et al, 2000; Santoso et al, 2002). Similarly, one study showed an association between the VNTR B/C genotype and the HPA-2B gene and CVD/CAD (Gonzalez-Conejero et al, 1998), whereas larger studies failed to confirm these findings (Carter et al, 1998; Baker et al, 2001). However, all these retrospective case– control studies only analysed survivors, introducing a survivor bias. Despite extensive studies in patients, only one small study in 40 subjects has examined the influence of these GpIba polymorphisms on platelet function (Cadroy et al, 2001). Hence, we evaluated the role of GpIba polymorphisms in platelet plug formation under pathophysiologically relevant high shear conditions. MATERIALS AND METHODS The study was approved by the Ethics Committee of the Vienna University. Written informed consent was obtained from all subjects. Healthy individuals (n ¼ 233; M/F ¼ 134/99; aged 33 ± 10 years) without any bleeding history, who had not regularly or recently (within the last 5 d) had an intake of cyclooxygenase inhibitors were studied. High-shear- induced (5000/s to 6000/s) platelet plug formation was tested using a platelet function analyser (PFA-100; Dade Behring, Marburg, Germany) to determine the collagen– adrenaline closure time (CEPI-CT). Single determinations were performed in one batch of cartridges, and individual day-to-day variability of CEPI-CT averaged 9% (Jilma, 2001). Collagen adenosine diphosphate (CADP)-induced platelet plug formation was not measured, because we have previously shown a very good correlation between Correspondence: Bernd Jilma, MD, Department of Clinical Phar- macology, or Petra Jilma, MD, Transfusion Medicine, Wa ¨hringer Gu ¨ rtel 18–20, A-1090 Wien, Austria. E-mail: Bernd.Jilma@univie. ac.at British Journal of Haematology, 2003, 120, 652–655 652 Ó 2003 Blackwell Publishing Ltd