Relation Between Red Blood Cell Distribution Width and Inflammatory Biomarkers in a Large Cohort of Unselected Outpatients (Report‪)‬

Recent investigations of atherosclerosis have focused on inflammation, providing new insight into mechanisms of disease. (1) In particular, current views regard atherosclerosis as a dynamic and progressive disease arising from the combination of endothelial dysfunction and inflammation. (2) Accumulating evidence suggests that circulating high-sensitivity C-reactive protein (hsCRP) represents one of the strongest predictors of cardiovascular morbidity and mortality in a number of settings. Indeed, hsCRP is currently the best validated inflammatory biomarker, since it appears to be a stronger predictor than total cholesterol, and it adds prognostic value to the Framingham risk score assessment. (1,3) The link between hsCRP and atherosclerosis was initially suggested to be that of a biomarker versus a mediator of atherosclerosis. This dog ma has been recently revisited, with observations from our group and several others suggesting that CRP plays a key role in promoting atherosclerotic processes and endothelial cell activation and inflammation. (4) Circulating blood cells, including red blood cells (RBCs), white blood cells, and platelets, are counted and sized electronically by modern instruments. The electronic counters not only register the total cell count but also estimate the average cell volume and the variation in cell size. In the context of RBCs, for example, these measurements are referred to as the mean corpuscular volume (MCV) and the RBC distribution width (RDW), respectively. (5) Red blood cell distribution width is an automatically measured index of the heterogeneity of the erythrocytes that is calculated by dividing the standard deviation (SD) of RBC volume by MCV and multiplying by 100 to express the result as a percentage. (6) A high RDW is generally set at greater than 14%, which corresponds to the 95th percentile of RDW for the reference population in the National Health and Nutrition Examination Survey III study. (6) Elevated RDW indicates a greater difference in size among RBCs, and when accompanied by a low MCV is indicative of iron deficiency, whereas normal RDW with low MCV is indicative of thalassemia. (5) Very recently, RDW was found to be a strong, independent predictor of morbidity and mortality in 2 large contemporary heart failure populations. (7) Moreover, Tonelli et al (8) found that an increased RDW is strongly and independently associated with the risk of cardiovascular morbidity and mortality in patients with prior myocardial infarction; they hypothesized that higher RDW levels might reflect an underlying chronic inflammation, which would result in an increased risk of cardiovascular disease (CVD). (8) However, this attractive hypothesis remains still to be proven.