Algorithm for whole blood viscosity: implication for antiplatelet bleeding risk assessment

A series of evaluations on whole blood viscosity (WBV) issues tried to elucidate the sensitivity, specificity and usefulness of the laboratory parameter in clinical practice. The aim of this article is to postulate (1) how to use routine clinical laboratory tests to derive WBV, and (2) the usefulness of WBV in evidence-based practice for determination of the therapeutic risk of bleeding. The study used 10 years of archived clinical pathology data from South West Pathology. WBV was derived from calculations incorporating haematocrit and total protein and extrapolation chart and reference values were developed. Association of and/or changes in WBV level with acetylsalicylates, C-reactive protein (CRP), D-dimer, Erythrocyte Sedimentation Rate (ESR), Faecal Occult Blood (FOB), homocysteine, International Normalised Ratio (INR), leucocytosis, leukapheresis, and platelet levels were determined. Whether there are differences between grades of WBV levels in the laboratory indices of diabetes, dyslipidaemia and renal function test were also investigated. A comparison with diagnostic digital method was also performed. One possible false assumption is that WBV (akin to CRP and ESR) is too sensitive and not a specific marker for the diagnosis of a pathological condition. Our findings may refute this notion. Interestingly, lower WBV levels are significantly associated with higher INR and acetylsalicylate levels. The observations from this study also elucidate the potential of WBV for evidence-based pathology to support a decision of antiplatelet medication, akin to INR in anticoagulant therapy. The clinical laboratory method postulated here can be performed in any facility that performs routine biochemistry and haematology.