Red blood cell distribution width is useful in discriminating adult onset Still's disease and sepsis within 24 hours after hospitalization

Background/Aims: Red blood cell distribution width (RDW) is a value representing the heterogeneity in the size of red blood cell, and it is usually used in distinguishing types of anaemia. Recently, it was reported that it could reflect the burden of inflammation in diverse diseases and their prognosis. Hence, in this study, we investigated whether RDW may contribute to discriminating adult onset Still's disease (AOSD) from sepsis in serious febrile patients within 24 hours after hospitalization. Methods: We reviewed the medical records and enrolled 21 AOSD patients, 27 sepsis patients and 30 matched healthy controls. We collected at least two laboratory results of variables including RDW within 24 hours after hospitalization, and we calculated their mean values. Results: Sepsis patients showed the significantly increased median white blood cell count, compared to AOSD patients ($14,390.0/mm^3$ vs. $12,390.0/mm^3$, p = 0.010). The median RDW in sepsis patients was higher than that in AOSD patients (15.0% vs. 13.3%, p = 0.001), and furthermore, the median RDW in both patient-groups was significantly higher than that in healthy controls. In contrast, the median ferritin level in sepsis patients was lower than that in AOSD patients (544.0 mg/dL vs. 3,756.6 mg/dL, p = 0.001). In multivariate analysis, RDW ${\geq}14.8%$ (odds ratio, 17.549) and ferritin < 2,251.0 mg/dL (odds ratio, 32.414) independently suggested sepsis more than AOSD in patients initially presenting with fever requiring hospitalization. Conclusions: RDW might be a rapid and helpful marker for a differential diagnosis between AOSD from sepsis at an early phase.