Elevated RDW Correlated With Increased Mortality in COVID-19 Patients

Blood vessel with blood cells, computer illustration. Red blood cells and white blood cells inside a blood vessel.
Study authors assessed the association between elevated and increasing red blood cell distribution width and increased mortality risk in patients with COVID-19.

Elevated and increasing red blood cell distribution width (RDW) may be associated with increased mortality risk in patients infected with coronavirus disease 2019 (COVID-19), according to a study recently published in JAMA Network Open.

Elevated RDW is associated with an increased risk for all-cause morbidity and mortality from many diseases, which suggests that RDW may be a nonspecific marker of illness and may be able to provide a robust risk-stratification among patients with the same acute illness. In this cohort study, study authors investigated whether there was an existing association between elevated RDW at hospital admission and mortality risk in COVID-19 patients.

In total, 1641 adult patients who were diagnosed with SARS-CoV-2 infection and admitted to 1 of 4 hospitals in Boston, Massachusetts, from March 2020 through April 2020 were included. The main outcome of the study was patient survival during hospitalization, measured by RDW at admission and during hospitalization.

Patient demographics included a mean (standard deviation) age of 62 (±18) years, 886 (54%) patients were men, 740 (45%) patients were White, and 497 (30%) patients were Hispanic. Throughout the study, 276 (17%) of patients died.

Study results suggest that both an elevated RDW, defined as RDW greater than 14.5%, at hospitalization and an increase in RDW during hospitalization are associated with an increased risk of mortality. The RR for the entire cohort was 2.73 (95% CI, 2.52-2.94; P <.001). Of the 1173 patients with normal RDW, mortality rate in this cohort was 11%; of the 468 patients with elevated RDW, mortality rate in this cohort was 31%.

While elevated RDW was associated with increased mortality in all ages, higher mortality risk ratios were observed in patients less than 70 years. This association was also seen after Cox proportional hazard models adjusted for absolute lymphocyte count, age, D-dimer level, and common comorbidities (hazard ratio [HR], 1.09 per 0.5% RDW increase; HR, 2.01 for RDW >14.5 vs ≤14.5; P <.001).

Mortality risk increased when RDW increased during hospitalization. When RDW was normal at hospitalization but increased during hospitalization, mortality increased from 6% to 24%; when RDW was elevated at hospitalization and increased during hospitalization, mortality increased from 22% to 40%.

Limitations of the study include results not being applicable to individuals with COVID-19 who are not hospitalized, results not being specific to any disease progression time points, and the study being underpowered for evaluation of mortality risk in Black populations.

“[A]n elevated RDW measured at admission and increasing RDW during hospitalization were associated with significantly higher mortality risk for patients with SARS-CoV-2 infection; RDW may be helpful for patient risk stratification,” concluded the study authors.


Foy BH, Carlson JCT, Reinertsen E, et al. Association of red blood cell distribution width with mortality risk in hospitalized adults with SARS-CoV-2 infection. JAMA Netw Open. 2020;3(9):e2022058. doi:10.1001/jamanetworkopen.2020.22058.