Hematological indices as predictors of in-hospital adverse outcomes in patients with COVID-19

The SARS-CoV-2 pandemic required medical teams to make rational decisions with limited resources, especially in Brazil. Various diagnostic tools, clinical guidelines, and existing indices were adopted to predict the risk of death and other adverse outcomes. The objective of this study was to validate three hematological indices [neutrophil-lymphocyte ratio (NLR), platelet-lymphocyte ratio (PLR), and lymphocyte-monocyte ratio (LMR)] for predicting adverse hospital outcomes in patients with COVID-19 in an observational cohort at a hospital in northeastern Brazil between April 2020 and October 2021. Hematological indices were calculated based on admission blood counts and correlated with hospital outcomes: in-hospital death, invasive mechanical ventilation, and renal replacement therapy. The analysis determined the frequencies of outcomes, established index thresholds, and assessed their association and accuracy and factors associated with hospital survival. Intra-hospital outcomes reflected disease severity; 34.62% of patients required admission to the ICU, 26.21% invasive mechanical ventilation, 4.2% renal replacement therapy, and 21.04% died. Advanced age, ICU requirement, and higher NLR were associated with higher risk of death. Multivariate analysis identified NLR as the only index associated with worse prognosis, with a cutoff point of 5.24 at hospital admission, showing a sensitivity of 84.0% and accuracy of 86.9%. The negative predictive value of 95.52% was highly significant, assisting hospital management by focusing efforts on higher-risk patients. These findings highlight the predictive value of the NLR, PLR, and LMR indices as valuable markers for risk stratification in patients hospitalized with COVID-19, offering a broader view of prognosis and guiding more personalized management and care strategies.