Association between red blood cell distribution width and mortality and severity among patients with COVID-19: A systematic review and meta-analysis.

Emerging evidence has underscored the potential usefulness of red blood cell distribution width (RDW) measurement in predicting the mortality and disease severity of COVID-19. This study aimed to assess the association of the plasma RDW levels with adverse prognosis in COVID-19 patients. A comprehensive literature search from inception to September 2020 was performed to harvest original studies reporting RDW on admission and clinical outcomes among patients hospitalized with COVID-19. RDW levels were compared between cases (patients who died or developed more severe symptoms) and controls (patients who survived or developed less severe symptoms). A total of 14,866 subjects from 10 studies were included in the meta-analysis. Higher levels of RDW were associated with adverse outcomes in COVID-19 patients (mean differences = 0.72; 95% CI = 0.47-0.97; I2  = 89.51%). Deceased patients had higher levels of RDW compared to patients who survived (mean differences = 0.93; 95% CI = 0.63-1.23; I2  = 85.58%). Severely ill COVID-19 patients showed higher levels of RDW, as opposed to patients classified to have milder symptoms (mean differences = 0.61; 95% CI = 0.28-0.94; I2  = 82.18%). Elevated RDW levels were associated with adverse outcomes in COVID-19 patients. This finding warrants further research on whether RDW could be utilized as a simple and reliable biomarker for predicting COVID-19 severity and whether RDW is mechanistically linked with COVID-19 pathophysiology.