Association between Changes in Haematological Parameters and Mortality in Patients Hospitalized Due to Severe COVID-19 in a Peruvian Reference Hospital

Objective: To determine the association between changes in haematological parameters and mortality in patients hospitalized due to severe COVID-19 at a Peruvian reference hospital from April to December 2020. Materials and Methods: Observational, analytical, historical cohort study based on the review of clinical records of patients hospitalized due to severe COVID-19 from April to December 2020. We evaluated changes in common haematological parameters, including white blood cells (WBCs), lymphocytes, neutrophils, and platelet counts, as well as the neutrophil-to-lymphocyte ratio (NLR) on the third and seventh days of hospitalization compared with admission values in the deceased and non-deceased groups. Changes in haematological parameters were expressed as median and interquartile ranges (IQR). Multivariate Poisson regression analysis was further done to evaluate the effect of haematological changes in mortality, adjusting for gender, age, and comorbidities. Results: We included 1033 cases, of which 68.05% were male. Deceased patients had a significant increase in total WBC on the third day (1.0 *10³/µL; IQR -1.7 to 5.4) and the seventh day (1.6*10³/µL; IQR -1.9 to 4.9) compared to their admission values. The neutrophil count in the deceased patients also increased on the third day (1.2; IQR -1.7 to 4.9) and seventh day (1.9; IQR-1.5 to 5.8), as did the NLR ratio on the third day (0.2; IQR -0.4 to 1.6) and seventh day (0.7; IQR -0.2 to 2.2). Surviving patients showed an opposite trend in these parameters. In contrast, platelet counts increased on the third day (49*10⁵/µL; IQR -0.3 to 1.3) and the seventh day (90*10⁵; IQR 0.0 to 2.0) in surviving patients, whereas deceased patients did not show significant changes. All these differences remained statistically significant in the adjusted analysis. Conclusion: An increase in total WBC, neutrophils, and NLR at the third and seventh days compared to admission values was associated with higher mortality in patients hospitalized due to COVID-19, while an increase in platelet count was associated with decreased mortality. Monitoring these changes can help in identifying those patients with higher mortality risk.