Shear-induced Filter Blockage. A Population Based Appraisal of a Method for the Assessment of Platelet, White Cell and von Willebrand Factor Interactions

Replication and hematological characterization of human platelet reactivity genetic associations in men from the Caerphilly Prospective Study (CaPS)

Platelet reactivity, an important factor in hemostasis and chronic disease, has widespread inter-individual variability with a substantial genetic contribution. Previously, our group performed a genome-wide association study of platelet reactivity identifying single nucleotide polymorphisms (SNPs) associated with ADP- and epinephrine- induced aggregation, including SNPs in MRVI1, PIK3CG, JMJD1C, and PEAR1, among others. Here, we assessed the association of these previously identified SNPs with ADP-, thrombin-, and shear- induced platelet aggregation. Additionally, we sought to expand the association of these SNPs with blood cell counts and hemostatic factors. To accomplish this, we examined the association of 12 SNPs with seven platelet reactivity and various hematological measures in 1300 middle-aged men in the Caerphilly Prospective Study. Nine of the examined SNPs showed at least suggestive association with platelet reactivity. The strongest associations were with rs12566888 in PEAR1 to ADP-induced (p = 1.51 × 10(-7)) and thrombin-induced (p = 1.91 × 10(-6)) reactivity in platelet rich plasma. Our results indicate PEAR1 functions in a relatively agonist independent manner, possibly through subsequent intracellular propagation of platelet activation. rs10761741 in JMJD1C showed suggestive association with ADP-induced reactivity (p = 1.35 × 10(-3)), but its strongest associations were with platelet-related cell counts (p = 1.30 × 10(-9)). These associations indicate variation in JMJD1C influences pathways that modulate platelet development as well as those that affect reactivity. Associations with other blood cell counts and hemostatic factors were generally weaker among the tested SNPs, indicating a specificity of these SNPs' function to platelets. Future genome-wide analyses will further assess association of these genes and identify new genes important to platelet biology.

Platelet tests in the prediction of myocardial infarction and ischaemic stroke: evidence from the Caerphilly Prospective Study

A platelet test that is predictive of myocardial infarction (MI) and/or stroke would enable the targeting of anti-platelet drugs towards high-risk patients. The predictive power of several platelet tests for MI and for stroke was examined in 2000 older men in the Caerphilly Cohort Study of Heart Disease, Stroke and Cognitive Decline. The tests were: aggregation to adenosine diphosphate (ADP) in platelet-rich plasma (PRP); aggregation to ADP in whole blood measured using an impedance method and a test of platelet aggregation induced in whole blood by high-shear flow. Around 200 MIs and 100 ischaemic strokes occurred during a 10-year follow-up. Neither primary nor secondary aggregation in PRP was predictive of MI. However, the fifth of men in whom the primary response to ADP was least, showed the highest risk of a subsequent stroke [relative odds (RO) 1.64; 95% confidence interval (CI) 1.12-2.43]. Aggregation in whole blood was not predictive of MI but, again, the fifth of men with the least platelet response showed the highest stroke incidence (RO 1.79; 95% CI 1.06-3.00). Retention of platelets in the high-shear test was not predictive of either event.