A U‐shaped association between baseline neutrophil count and COVID‐19‐related mortality: A retrospective cohort study

Abstract

Background Several descriptive studies have reported that higher neutrophil count (NC) may be correlated with poor prognosis in patients with confirmed COVID‐19 infection. However, the findings from these studies are limited by methodology and data analysis. Methods This study is a cohort study. We non‐selectively and consecutively collected a total of 663 participants in a Chinese hospital from January 7 to February 28. Standardized and two‐piecewise Cox regression model were employed to evaluated the association between baseline neutrophil count (bNC), NC change rate (NCR), and death. Results bNC had a U‐shaped association with death. In the range of 0.1 to ≤1.49×10⁹ /L (HR = 0.19, 95% CI = 0.05 to 0.66) and > 3.55×10⁹ /L of bNC (HR = 2.82, 95% CI = 1.19 to 6.67), the trends on bNC with mortality were opposite. By recursive algorithm, the bNC at which the risk of the death was lower was range of >1.49 to ≤3.55×10⁹ /L (HR=13.64, 95%CI=0.25 to 74.71). In addition, we find NCRs (NCR1 and NCR2) is not associated with COVID‐19‐related deaths. Conclusions Compared with NCR, bNC has the potential to be used for early risk stratification in patients with COVID‐19 infection. The relationship between bNC and mortality was U‐shaped. The safe range of bNC was 1.64 to 4.0 ×10⁹ /L. Identifying the correlation may be helpful for early risk stratification and medical decision making.