STARD-compliant article: The utility of red cell distribution width to predict mortality for septic patients visiting the emergency department

Abstract

Sepsis is a common condition in the emergency department that is associated with high mortality. Red blood cell distribution width (RDW) has been used as a simple prognosis predictor for patients with community-acquired pneumonia, gram-negative bacteremia, and severe sepsis or septic shock. To evaluate the performance of RDW to predict in-hospital mortality among septic patients, we conducted a hospital-based retrospective cohort study in an emergency department of a tertiary teaching hospital. RDW was compared with other commonly used clinical prediction scores (Systemic Inflammatory Response Syndrome (SIRS), Mortality in Emergency Department Sepsis (MEDS) and the Confusion, Urea nitrogen, Respiratory rate, Blood pressure, 65 years of age and older (CURB65)). Of 6973 consecutive adult patients with a clinical diagnosis of sepsis and 2 sets of blood culture ordered by physicians, 477 (6.8%) died. The mortality group had higher RDW levels than the survival group (15.7% vs 13.8%). After dividing RDW into quartiles, the patients in the highest RDW quartile (RDW >15.6%; mortality, 16.7%) had more than twice the risk of in-hospital mortality compared with patients in the second highest quartile (RDW >14% and <15.6%; mortality, 7.3%), whereas the mortality rate in the lowest RDW quartile (<13.1%) was only 1.6%. The area under the receiver operating characteristic curve of RDW to predict mortality was 0.75 (95% confidence interval, 0.72-0.77), which is significantly higher than the areas under the curve of clinical prediction rules (SIRS, MEDS, and CURB65). After integrating RDW into these scores, all scores performed better in predicting mortality (0.73, 0.72, and 0.77, for SIRS, MEDS, and CURB65, respectively). RDW could be an independent predictor of mortality among septic patients. Clinicians could classify the septic patients into different risk groups according to RDW quartiles. For more accurate mortality prediction, RDW could be a potential parameter to be incorporated into clinical prediction rules.

Figure 1

Flow chart of subject inclusion.

Figure 2

Mortality distribution in RDW quartiles. CI = confidence interval, RDW = red blood cell distribution width.

Figure 3

Receiver operating characteristic (ROC) curves. Comparison of the performance of RDW as a continuous variable in predicting mortality with clinical prediction rules (A) and common biomarkers utilized clinically (B). ROC curves of RDW as a quartile indicator with and without clinical prediction rules (C) and in the severely septic group (D). CRP = C-reactive protein, CURB65 = Confusion, Urea nitrogen, Respiratory rate, Blood pressure, 65 years of age and older score, MEDS = Mortality of Emergency Department Sepsis score, PCT = procalcitonin, RDW = red blood cell distribution width, RDWQ = RDW in quartile form, SIRS = Systemic Inflammatory Response Syndrome.