Can red cell distribution width predict acute mesenteric ischemia?

Abstract

To the Editor, We read with great interest the article by Kisaoglu et al. [1] who studied the association between red cell distribution width (RDW) and acute mesenteric ischemia (AMI). The authors concluded that RDW on admission was of marginal help to diagnose AMI among patients with abdominal pain. RDW is a simple, accessible, and cheap parameter which is a measure of erythrocyte size variability [2]. Although promising, it has raised more questions than it has answered. First, any incidence that induces the release of reticulocytes into the circulation will result in an increase in RDW, such as anemia, renal/hepatic dysfunction, thyroid disease, transfusion, acute or chronic inflammation, neurohumoural activation, malnutrition (i.e., iron, vitamin B12, and folic acid), ethnicity, bone marrow depression, and use of some medications (i.e., erythropoietin use and antibiotic use) [2]. AMI is an illness that mostly happens in elderly patients who may develop multiple comorbidities, which may significantly affect RDW level [1]. In the present study, the authors did not describe the above-mentioned influencing factors in a detailed way which would mask the real relationship between RDW and AMI. Second, it would be better if the authors defined the time elapsed between blood sampling and RDW measuring since the RDW level may be altered after a delay [2]. Third, only 159 patients were included in this study, thus there was no enough statistical power to discriminate all included covariates listed in Table 1 [1, 3]. Meanwhile in the Result section, the authors did not report the odds ratio of RDW for AMI in multivariate logistic regression analyses. We used Bayes’ theorem to calculate the probability of AMI, conditioned by the likelihood ratio as a function of the pretest probability (49/159) [4]. The results showed that when RDW [15.04 %, the post-test probability of AMI was 49 %; and when RDW\15.04 %, the post-test probability of AMI was 0.25 %. However, it has been reported that a confirmation strategy can be accurate enough to diagnose a disease when the post-test probability was above 85 %, and that for an exclusion strategy, it was below 5 % [5]. Therefore, RDW seems to be useless for the accurate diagnosis of AMI. Fourth, in the present study, the authors found there was no relation between RDW and mortality/size of lesion which is inconsistent with the results of another study by Bilgic et al [6]. It would be better if the authors explained the reason for these inconsistent results. Finally, there was no comparison of RDW and other prediction models (SAPS) made in this study. Moreover, whether addition of RDW in the previous prediction models or the combination of RDW with other parameters may improve diagnostic accuracy was unknown. However, as subjected to its purpose, further investigations may help to answer the questions raised herein. Although RDW seems to be a promising parameter for the diagnosis of AMI, further researches are needed to determine its clinical value. L. Jiang Y. Ma M. Zhang (&) Department of Emergency Medicine, Second Affiliated Hospital, School of Medicine and Institute of Emergency Medicine, Zhejiang University, Jiefang road 88, Hangzhou, China e-mail: zmhz@hotmail.com