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

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 COVID-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 ( I 2 : 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.