Whole blood viscosity assessment issues III: Association with international normalized ratio and thrombocytopenia

BACKGROUND: Anticoagulant and antiplatelet therapies are being used interchangeably or in combination. While international normalized ratio is assessed to determine anticoagulant's contraindication/need, whole blood viscosity is not assessed to determine the need for antiplatelet. AIMS: The objective of this study is to investigate whether whole blood viscosity value is associated with levels of international normalized ratio and platelet count. MATERIALS AND METHODS: De-identified archived clinical pathology data for the year 2008 were audited. All cases of international normalized ratio, which were concomitantly tested for haematocrit and total proteins, were extracted (n=7,387). Whole blood viscosity levels were extrapolated. Whether differences are associated with normal vs. high international normalized ratio and thrombocytopenia vs. thrombocytosis were evaluated. RESULTS: Multivariate analysis show that whole blood viscosity levels statistically significantly differs between international normalized ratio and platelet counts (p<0.001). Platelet count is statistically significantly lower in low blood viscosity when compared with hyperviscosity and normoviscosity (p<0.001). Conversely, international normalized ratio is statistically significantly higher in low blood viscosity relative to hyperviscosity (p<0.001) and normoviscosity (p<0.002). No difference was observed between hyperviscosity and normoviscosity in platelet count or international normalized ratio. CONCLUSION: The observation corroborates with previous reports to suggest putting into perspective the specificity of whole blood viscosity relative to stasis, against which antiplatelet is employed. It indicates that low whole blood viscosity is synonymous to high international normalized ratio whereby anticoagulant and antiplatelet therapies are contraindicated. International normalized ratio, platelet count and blood viscosity are laboratory indices to consider in constituting antiplatelet monitoring panel.