The association of Red cell distribution width and in-hospital mortality in older adults admitted to the emergency department

Kim et al. Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine The association of Red cell distribution width and in-hospital mortality in older adults admitted to the emergency department Soo Hyun Kim Jeong Hoon Yeon Kyu Nam Park Sang Hoon Oh Seung Pill Choi Young Min Kim Han Joon Kim Chun Song Youn Background: The objective of the study was to test the hypothesis that elevated red cell distribution width (RDW) at admission increases the risk of mortality in older patients admitted to the emergency department (ED). Methods: We performed a retrospective analysis of patients admitted to the ED between May 2013 and October 2013. We included patients who were older than 65 years who visited the ED with any medical problems. Baseline RDW values were measured at the time of admission to the ED. The primary outcome was all-cause in-hospital mortality. Multivariate logistic analysis was performed. Results: A total of 1,990 patients were finally included in this study. The mean age was 75 years (SD 7), and 936 (47 %) subjects were male. The in-hospital mortality rate was 3.76 % (74 patients). RDW values higher in non-survivors than in survivors (15.9 ± 2.5 vs. 13.8 ± 1.7, p < 0.001). Multivariate logistic analysis showed that RDW was associated with all-cause in-hospital mortality after adjusting for other confounding factors. Discussion: RDW value at admission is an independent predictor of all-cause in-hospital mortality among patients older than 65 years. After adjustment for multiple confounders, the all-cause in-hospital mortality rate increased by 21.8% for each 1% increase in RDW. Conclusion: These results show that RDW at admission is associated with in-hospital mortality among patients older than 65. Thus, RDW at admission may represent a surrogate marker of disease severity. We caution against using these findings to aid clinical decision-making process until they are externally validated. Mortality; Older adults; Erythrocyte indices Background The proportion of elderly individuals in the population is increasing, and older people visit the emergency department (ED) more frequently than younger adults [ 1–4 ]. Older patients often present with atypical signs and symptoms and have multiple comorbidities that complicate accurate diagnosis and treatment [5]. Furthermore, these patients have a higher level of acuity, higher risk for hospitalization and higher intensive care unit (ICU) admission rate [ 6–9 ]. However, there are few studies measuring the association between the risk factors and in-hospital mortality in older patients admitted to the ED. Red cell distribution width (RDW) is a quantitative measure of variability in the size of circulating erythrocytes and is routinely reported to physicians in clinical practice as part of the automated complete blood count (CBC). RDW is used as an ancillary test to help diagnose different types of anemia. Recent studies have shown that higher RDW is associated with increased mortality risk in different clinical settings such as clinically significant cardiovascular disease, stroke, septic shock, bacteremia and community-acquired pneumonia [ 10–15 ]. Although the exact mechanisms that underlie the association between RDW and mortality are unknown, high RDW may have an association with the presence of an ongoing disease process, such as inflammation, tissue hypoperfusion, oxidative stress, or renal failure [16]. RDW is known to be a strong predictor of mortality in the general population of middle-aged and older adults [ 16, 17 ] and is also considered an age-associated prognostic biomarker in adults aged 45 and older [17]. However, the prognostic value of RDW in older patients admitted to the ED has rarely been investigated. In addition, older adults admitted to the ED are likely to have multiple comorbidities. We tested the hypothesis that elevated RDW at admission increases the risk of mortality in older patients admitted to the ED. We assessed the association between RDW at admission and in-hospital mortality in older patients admitted to the ED. Methods Study design This was a retrospective, observational study of a consecutive cohort admitted to a large urban ED in Seoul, Korea. Our Institutional Review Board approved this study, and waiver of consent was allowed because of its retrospective nature. Study setting and population This study was conducted in the Department of Emergency Medicine of the Seoul St. Mary’s Hospital, a 1,320-bed tertiary teaching hospital. Our ED serves an annual census of approximately 60,000 patients. The emergency physician provides initial treatment to all adult emergency patients. We included patients older than 65 years who visited the ED with any medical problems between May 2013 and October 2013. Patients were excluded if they had a traumarelated injury; had a hematologic disease such as leukemia, myelodysplastic syndromes, myeloproliferative disease, myelofibrosis or agranulocytosis; were (...truncated)