Anisocytosis is Associated With Short-Term Mortality in COVID-19 and May Reflect Proinflammatory Signature in Uninfected Ambulatory Adults

Abstract

Background: Red cell distribution width (RDW), a measure of anisocytosis, is observed in chronic inflammation and is a prognostic marker in critically ill patients without COVID-19, but data in COVID-19 are limited.

Methods: Between March 12 and April 19, 2020, 282 individuals with confirmed COVID-19 and RDW available within 7 days prior to COVID-19 confirmation were evaluated. Individuals were grouped by quartiles of RDW. Association between quartiles of RDW and mortality was assessed using the Kaplan-Meier method and statistical significance was assessed using the log-rank test. The association between RDW and all-cause mortality was further assessed using a Cox proportional hazards model. Plasma cytokine levels in uninfected ambulatory adults without cardiovascular disease (n=38) were measured and bivariate Spearman correlations and principle components analysis were used to identify relationships between cytokine concentrations with RDW.

Results: After adjusting for age, sex, race, cardiovascular disease, and hemoglobin, there was an association between RDW and mortality (Quartile 4 vs Quartile 1: HR 4.04 [1.08-15.07]), with each 1% increment in RDW associated with a 39% increased rate of mortality (HR 1.39 [1.21-1.59]). Remote RDW was also associated with mortality after COVID-19 infection. Among uninfected ambulatory adults without cardiovascular disease, RDW was associated with elevated pro-inflammatory cytokines (TNF-α, IL8, IL6, IL1b), but not regulatory cytokines (TGFb).

Conclusions: Anisocytosis predicts short-term mortality in COVID-19 patients, often predates viral exposure, and may be related to a pro-inflammatory phenotype. Additional study of whether the RDW can assist in the early identification of pending cytokine storm is warranted.

Keywords: Anisocytosis; Covid-19; Critical Illness; Cytokines; Erythrocyte Indices; Prognosis; RDW.

Figure 1.

Association Between Continuous RDW and Mortality (A) unadjusted Kaplan-Meier curves, (B) unadjusted Cox regression model with RDW modelled using a penalized smoothed spline, (C) penalized-smoothed spline modelled age and RDW (color code represents log (Hazard Ratio) of mortality). Red demonstrates higher hazards of mortality and blue demonstrates lower hazards of mortality. This is modelled by age and RDW showing that 2% increase in RDW is equivalent to 10 year age increase with respect to mortality (D) Receiver Operating Characteristic curve for RDW to predict 30-day mortality (using Kaplan-Meier method) Abbreviations: HR=hazard ratio; RDW=red cell distribution width; TP = true positive rate; FP = false positive rate; AUC=area under the curve

Figure 2.

Forest Plot Depicting the Association Between Quartiles of Acute RDW and Mortality in Three Models Unadjusted; Model 1 (adjusted for age, sex, race); Model 2 (adjusted for age, sex, race, cardiovascular disease, and hemoglobin)

Figure 3.

Remote RDW Is Associated With Acute RDW and Mortality (A) Change in RDW (remote to acute) in COVID-19 infected patients, (B) Kaplan-Meier test of mortality in COVID-19 infections

Figure 4.

Anisocytosis in 38 Uninfected Ambulatory Adults Without Cardiovascular Disease Is Associated With a Pro-inflammatory Milieu (A) correlation matrix between RDW and cytokine profile (Spearman correlations: *P<0.05, **P<0.01), (B) hierarchical clustering showing that RDW clusters with IL1-beta, IL-6, and TNF-alpha, (C) Component plot showing that RDW clusters with TNF-alpha and IL1-beta, (D) Principal Component Analyses showing that RDW clusters with IL-1beta, TNF-alpha, and IL-8