Is erythrocyte sedimentation rate a useful inflammatory marker independently of the hematocrit? Comparison results with plasma viscosity

Plasma viscosity (PV) and erythrocyte sedimentation rate (ESR) are tests which can be used as inflammation and tissue injury markers [2, 11]. ESR usage is more extended than PV in clinical laboratories. However ESR may be haematocrit (Ht) dependent and is related with red blood cell (RBC) rheological properties [1], whereas RBC are not involved in PV. We aimed to evaluate retrospectively the impact of Ht on ESR as an inflammatory marker and compare the results with those of PV in 333 outand in-patients at our hospital. Our study is a human non-interventional retrospective review and written consent is not required for human non-interventional studies. We evaluated both markers in two patient groups of i.e., the first one did not present other inflammatory components measured as C-reactive protein (CRP) below 10 mg/L and fibrinogen below 450 mg/dL (n= 211). The second one presented CRP over 10 mg/L and/or fibrinogen values higher than 450 mg/dL (n= 122). PV and ESR were determined in a capillary plasma viscosimeter (Fresenius GmbH, Germany) at 37◦C and using a Ves matic 30 Plus Analyzer (Diesse Diagnostica Senese, Siena, Italy), respectively. CRP was determined by immunoturbidity in an AU5430 autoanalyzer (Beckman Coulter, Lexington, KY, USA) and fibrinogen analysis was performed in an ACL-TOP 700 autoanalyzer (Instrumentation Laboratory, Bedford, MA, USA).