To the editor: We read the article by Ma et al1 with a great interest. They aimed to investigate the potential correlation of red cell distribution width (RDW) with the severity of coronary artery disease (CAD) in a large Chinese cohort from a single center. They concluded that the RDW level was significantly higher in patients with CAD than that in normal controls, and the baseline RDW level was an independent predictor for CAD and the severity of coronary stenosis.
RDW is a standard laboratory parameter that represents variation in red blood cell size on a standard hemogram and is frequently used in evaluating blood diseases. RDW has recently been observed as an independent predictor of all-cause long-term mortality in patients with coronary artery disease. 2 Sometimes conditions like the differential diagnosis of anemias might effect RDW parameter and so this parameter might be changed in such any abnormality in thyroid function tests, renal or hepatic dysfunction (creatinine >1.5 mg/dl, aspartate aminotransferase and alanine transaminase more than twice the upper limit of normal, respectively), inflammatory diseases, and any medication. On the other hand, it is also reported that an increased RDW is associated with nutritional deficiency (ie, iron, vitamin B12, and folic acid) and ethnicity.
RDW, an inexpensive and routinely measurable laboratory variable, may also predict CAD complexity. In previous study, the authors evaluated the relationship between RDW and severity of chronic heart disease (CHD) in patients with acute myocardial infarction. They analyzed the relation between RDW and angiographic severity of CAD. Patients with elevated Syntax score (SS) (>32) had higher RDW values. The SS was positively correlated with RDW. 3 Although current study is interesting and relatively well-presented, some principal points require to be further considered. First of all the extent of CAD was evaluated by calculation of Gensini scores in the present study. However the SS may be also developed for grading of coronary complexity based on angiographic visual assessment. The addition of clinical risk factors to the SS has been shown to potentially further augment its utility to objective evaluation for patients with severity of CAD. The Logistic Clinical SS consisting of four variables (SS, age, creatinine clearance (CrCl), left ventricular ejection fraction (LVEF)) fairly increases the risk stratification of CAD patients for long term all-cause mortality compared with the SS alone in previous study. The Logistic Clinical SS was able to accurately seperate patients with or without a clinical outcome and could accurately predict individual patient risk (calibration) without under or over-estimating risk. Involving in this score, renal dysfunction may predict CAD and could estimate the risk of mortality and morbidity for CAD. 3 Second we strongly believe that it would be better, if the authors gave information about interobserver and intraobserver variability for CAD severity in the current study. Additionally, the presence of non-alcoholic fatty liver disease (NAFLD) is associated with high severity of CAD. Patients with NAFLD should be closely followed up for the presence and severity of CAD. 4 The occurrence of CAD in elderly type 2 diabetes mellitus patients with microalbuminuria was higher than that in patients with normal albuminuria, and the severity of the disease also increased in patients with microalbuminuria.5 In this point of view, the authors had mentioned liver and kidney function tests, the results of the study might be useful and different. Finally, it would be better if the authors defined how much time they specified on measuring RDW levels, because of the delaying blood sampling can cause abnormal results in RDW measurements.
We believe that these findings will enlighten further studies about the relationships between RDW and severity of CAD. RDW itself alone without other inflammatory markers may not give information to clinicians about the inflammatory condition and prognostic indication of the patients. So, we think that it should be evaluated together with other serum inflammatory markers.
1. Ma FL, Li S, Li XL, Liu J, Qing P, Guo YL, et al. Correlation of red cell distribution width with the severity of coronary artery disease: a large Chinese cohort study from a single center. Chin Med J 2013; 126: 1053-1057.
2. Tonelli M, Sacks F, Arnold M, Moye L, Davis B, Pfeffer M. Relation between red blood cell distribution width and cardiovascular event rate in people with coronary disease. Circulation 2008; 117: 163-168.
3. Akin F, Köse N, Ayça B, Katkat F, Duran M, Uysal OK, et al. Relation between red cell distribution width and severity of coronary artery disease in patients with acute myocardial infarction. Angiology 2012; Epub ahead of print.
4. Sun L, Lü S. Association between non-alcoholic fatty liver disease and coronary artery disease severity. Chin Med J 2011; 124: 867-872.
5. Guo LX, Ma J, Cheng Y, Zhang LN, Li M. Urinary albumin excretion rate is correlated with severity of coronary artery disease in elderly type 2 diabetic patients. Chin Med J 2012; 125: 4181-4184.