Hematocrit alters VerifyNow P2Y12 assay results independently of intrinsic platelet reactivity and clopidogrel responsiveness
UMass Chan Affiliations
Department of Medicine, Division of Cardiovascular MedicineDocument Type
Journal ArticlePublication Date
2013-10-01Keywords
Adenosine DiphosphateAged
Blood Platelets
Female
*Hematocrit
Humans
Male
Middle Aged
Platelet Aggregation Inhibitors
Purinergic P2Y Receptor Antagonists
Receptors, Purinergic P2Y12
Ticlopidine
Cardiology
Cardiovascular Diseases
Hematology
Metadata
Show full item recordAbstract
BACKGROUND: The VerifyNow P2Y12 assay assesses the adequacy of clopidogrel therapy by measuring ADP-induced platelet activation in whole blood. Low hematocrit is associated with high clopidogrel on-treatment platelet reactivity (HTPR) defined by this assay. OBJECTIVES: To characterize the effect of hematocrit on VerifyNow values and determine if it is due to hematocrit-dependent changes in intrinsic platelet reactivity or an in vitro assay phenomenon. PATIENTS/METHODS: Adenosine diphosphate-induced platelet activation was measured using the VerifyNow P2Y12 assay, whole blood impedance and light transmission platelet aggregometry (LTA) before and after clopidogrel loading in 113 patients undergoing elective cardiac catheterization. Iso-TRAP-induced platelet activation was additionally measured using the VerifyNow device. Multivariate modeling employing clinical and laboratory variables was used to investigate the association between hematocrit and VerifyNow values. RESULTS: VerifyNow P2Y12 reaction units (PRU) and iso-TRAP Base units before and after clopidogrel loading, but not their relative change, exhibited strong negative correlation with hematocrit (P < /= 0.0005 for both). While hematocrit remained a strong predictor of post-clopidogrel PRU (P = 0.001) in multivariate modeling, it was independent of post-clopidogrel ADP-induced platelet reactivity as measured by LTA (P = 0.001). Correcting for the effects of hematocrit resulted in a 15-39% reduction in the prevalence of HTPR defined by thresholds of 208-236 PRU. CONCLUSIONS: The effect of hematocrit on VerifyNow PRU values is an in vitro phenomenon that is independent of intrinsic change in ADP-induced platelet reactivity and clopidogrel responsiveness. Correcting for hematocrit when using this assay may more accurately identify patients with HTPR that may benefit from alternative antiplatelet therapy.Source
J Thromb Haemost. 2013 Oct;11(10):1814-22. doi: 10.1111/jth.12376. Link to article on publisher's siteDOI
10.1111/jth.12376Permanent Link to this Item
http://hdl.handle.net/20.500.14038/30491PubMed ID
24118870Related Resources
Link to Article in PubMedae974a485f413a2113503eed53cd6c53
10.1111/jth.12376