Red Blood Cell Distribution Is a Significant Predictor of Severe Illness in Coronavirus Disease 2019

Introduction: As red blood cell distribution width (RDW) significantly predicts clinical outcomes in patients with respiratory tract infections and in those with critical illnesses, we performed a critical analysis of the literature to explore the potential prognostic role of this laboratory parameter in coronavirus disease 2019 (COVID-19). Methods: An electronic search was conducted in Medline, Scopus and Web of Science, using the keywords "coronavirus disease 2019" OR "COVID-19" AND "red blood cell distribution width" OR "RDW" in all fields, up to the present time, with no language restriction. Studies reporting the value of RDW-CV in CO-VID-19 patients with or without severe illness were included in a pooled analysis. Results: The pooled analysis included 3 studies, totaling 11,445 COVID-19 patients' samples (2,654 with severe disease; 23.2%). In all investigations RDW-CV was higher in COVID-19 patients with severe illness than in those with mild disease, with differences between 0.30 and 0.70%. The pooled analysis, despite consistent heterogeneity (I2: 88%), revealed that the absolute RDW-CV value was 0.69% higher (95% CI 0.40-0.98%; p < 0.001) in COVID-19 patients with severe illness compared to those with mild disease. Conclusion: These results, along with data published in other studies, support the use of RDW for assessing the risk of unfavorable COVID-19 progression.