Red Cell Distribution Width: A Predictor of All-Cause Mortality in Patients with Coronary Artery Disease

In a recent study, Sun et al. [1] aimed to investigate the association between red blood cell distribution width (RDW) and the risk of all-cause mortality in patients with ST-elevation myocardial infarction (STEMI), who were free of heart failure at baseline. They concluded that increased RDW is associated with all-cause and cardiac mortality in their STEMI patients. Their study provides important information on this clinically relevant condition. The ready availability of RDW at no additional costs may encourage its wider use in clinical practice in the future. Thanks to the authors for their contribution.Inflammation is a significant feature of arteriosclerotic disease, and the vulnerability of coronary plaques in acute myocardial infarction may be related to the levels of serum inflammatory indicators [2]. Some markers have been demonstrated to be associated with early and late complications in patients with acute myocardial infarction. Preprocedural serum inflammatory markers such as C-reactive protein may be associated with early complications and long-term outcome in patients undergoing a percutaneous coronary intervention [3]. Novel inflammatory markers have been considered as major risk factors predisposing to cardiovascular morbidity and mortality [4]. RDW is effectively a free test; it is reported alongside a complete blood count at no extra costs, with good prognostic value even compared with relatively expensive inflammatory markers.However, we have some minor comments on your paper. A number of studies have reported that elevated RDW levels are associated with a poor prognosis in the setting of stable angina, acute coronary syndrome, coronary bypass surgery, heart failure, stroke, peripheral arterial disease and older age [5]. RDW is a measure of the variability in the size of circulating red blood cells and is part of the complete blood count panel. It is a commonly used tool in the differential diagnosis of anemia and may be elevated in conditions where reticulocytes are released into the circulation. RDW is also independently associated with mortality in both the general population and in patients with certain diseases. RDW has recently been defined to highly correlate with short- and long-term outcomes in different clinical settings. However, RDW may also reflect ethnicity, neurohumoral activation, renal dysfunction, thyroid disease, bone marrow dysfunction, inflammatory diseases, chronic or acute systemic inflammation [6], medication use [7], hepatic dysfunction and nutritional deficiencies (i.e. iron, vitamin B12 and folic acid). A common underlying cause of high RDW is iron or B12/folate deficiency, where normal erythrocytes are mixed with smaller or larger ones produced during the state of deficiency. Increased RDW could also be due to hepatic dysfunction and excessive alcohol intake, which results in macrocytosis.In conclusion, we strongly believe that the findings reported by Sun et al. [1] will encourage further studies examining the relationship between RDW and STEMI. However, one should bear in mind that RDW as a stand-alone marker without other inflammatory indicators may not provide exact information on the inflammatory status to clinicians and on patient prognosis [8]. Therefore, from that point of view, we think that it should be evaluated concomitant with other serum inflammatory markers.The authors have no conflict of interests.