Original Contribution
Red cell distribution width is a prognostic factor in severe sepsis and septic shock

https://doi.org/10.1016/j.ajem.2012.10.017Get rights and content

Abstract

Objective

This study was performed to investigate the association of red cell distribution width (RDW) with 28-day mortality in patients with severe sepsis and septic shock.

Methods

We performed a retrospective analysis of patients with severe sepsis and septic shock. Patients' demographic data, comorbidities, the blood test results including RDW at admission to the emergency department, and Acute Physiologic and Chronic Health Evaluation II score were compared between 28-day survivors and nonsurvivors. Red cell distribution width was categorized into tertiles as 14% or less, 14.1% to 15.7%, and 15.8% or greater. Multivariate Cox proportional hazards regression analysis was performed to determine the risk factors for mortality.

Results

A total of 566 patients were included, and overall mortality was 29%. Red cell distribution width was significantly higher in nonsurvivors than in survivors, and the corresponding mortality of patients with an RDW of 14% or less, 14.1% to 15.7%, and 15.8% or greater was 13.1%, 30.1%, and 44.9%, respectively (P < .001). In Cox proportional hazards analysis, groups with higher RDW are independently associated with 28-day mortality compared with groups with an RDW of 14.0% or less: RDW 14.1% to 15.7% (hazard ratio, 1.66; 95% confidence interval [CI], 1.00-2.76) and RDW of 15.8% or greater (hazard ratio, 2.57; 95% CI, 1.53-4.34). The area under the receiver operating curve of RDW was 0.68 (95% CI, 0.63-0.72).

Conclusion

Red cell distribution width is associated with 28-day mortality in patients with severe sepsis and septic shock.

Introduction

Severe sepsis and septic shock are increasing in incidence, and the mortality rate is still elevated [1], [2]. The prediction of outcome for patients with sepsis may facilitate more aggressive interventions, and many prognostic factors such as age, sex, comorbidities, biomarkers, and severity of illness have been reported to be associated with outcome [3], [4], [5].

Red cell distribution width (RDW) is a measure of the variability in the size of circulating red blood cells and is a part of the complete blood count (CBC) panel. It is mainly used as a tool for the differential diagnosis of anemia and could be elevated in any conditions where reticulocytes are released into circulation.

Besides the evaluation of anemia, recent studies have reported that RDW is also associated with prognosis in patients with congestive heart failure, acute myocardial infarction, pulmonary embolism, pneumonia, critical illness, and cardiac arrest [6], [7], [8], [9], [10], [11]. The mechanism of elevated RDW in these patients is not known, but it has been suggested that inflammatory process is associated with elevated RDW. It has been reported that elevated RDW is associated with inflammatory markers such as interleukin-6 and tumor necrosis factor, and proinflammatory cytokines could suppress the maturation of red blood cells and decrease the half-life of red blood cells, which, in turn, results in an elevated RDW [10], [12], [13].

The inflammatory response is important to the pathophysiology of sepsis, but there are few studies about the RDW and sepsis. In a study of critically ill patients, higher frequency of sepsis was observed in groups with higher RDW, and elevated RDW was associated with bloodstream infection [10]. However, this study included the patients admitted to intensive care unit (ICU) and did not focus on the septic patients.

We hypothesized that RDW, as a marker of inflammation, may be associated with mortality in sepsis. Therefore, we performed this study to evaluate the relationship between RDW at admission and 28-day mortality in patients with severe sepsis and septic shock.

Section snippets

Study population

We performed a retrospective analysis of prospectively collected patients' data with severe sepsis and septic shock at an urban, tertiary care, emergency department with an annual census of approximately 70 000 between January 1, 2009, and December 31, 2011. The institutional review board approved this study.

We retrospectively analyzed the prospective data of adult patients older than 18 years who visited an emergency department and were diagnosed as having severe sepsis and septic shock.

Characteristics of study population

During the study period, a total of 590 patients were initially included. Of them, 24 patients were excluded because of withdrawal aggressive management. Therefore, 566 patients were included into the final analysis, and there was no loss to follow-up at 28 days.

The mean age of the enrolled patients was 70.0 ± 13.4 years, 314 (55.5%) were male, and 164 patients (29.0%) died during the 28-day follow-up period. Nonsurvivors were older and had more male patients (Table 1). The 3 most frequent

Discussion

In the present study, we observed that RDW of nonsurvivors was higher than that of survivors in severe sepsis and septic shock, and there was a graded association between RDW and 28-day mortality. In addition, RDW had a relationship with the severity of the patients and was an independent prognostic factor of 28-day mortality in patients with severe sepsis and septic shock.

The association of RDW with mortality was evaluated in patients with general cardiovascular diseases [17]. Subsequent

Limitations

The major limitation of the present study is a retrospective analysis of data in a single institution, and the results of this study might not be generalizable to other institutions. Second, RDW could be influenced by iron, folate, and vitamin B12, but we did not measure those variables. Third, this is a retrospective analysis, and the transfusion records of the patients before admission are not available. Last, the results of this study show the association of RDW with 28-day mortality but do

Conclusions

Red cell distribution width at admission is associated with 28-day mortality and severity of patients with severe sepsis and septic shock. Therefore, RDW could be used as a prognostic factor in severe sepsis and septic shock.

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