Neutrophil-to-Lymphocyte Ratio, Systemic Immune-Inflammation Index, and HALP Score as Predictors of Mortality in...

Background: Acute respiratory distress syndrome (ARDS) remains one of the most serious causes of respiratory failure and mortality in critically ill patients. Although the Berlin Definition provides a standardized framework for diagnosis, it offers limited predictive value for clinical outcomes. In this context, there is growing interest in the use of routinely available hematological markers as practical tools for early risk stratification. This study aimed to examine the association between hematological parameters and mortality in patients with ARDS, with particular emphasis on complete blood count-derived inflammatory indices. Methods: This multicenter retrospective cohort study included 404 adult patients with a confirmed diagnosis of ARDS who were admitted to intensive care units in Saudi Arabia. Demographic, clinical, and laboratory data were collected from electronic medical records. In addition to standard hematological parameters, the neutrophil-to-lymphocyte ratio (NLR), systemic immune-inflammation index (SII), and hemoglobin-albumin-lymphocyte-platelet (HALP) score were calculated from admission laboratory findings. Comparisons between survivors and non-survivors were performed using non-parametric statistical tests, and a receiver operating characteristic (ROC) curve analysis was used to evaluate the prognostic performance of these indices for in-hospital mortality. Results: Of the 404 included patients, 295 survived, and 109 died during hospitalization. Non-survivors demonstrated significantly higher white blood cell and neutrophil counts, alongside significantly lower lymphocyte, eosinophil, hemoglobin, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, and albumin levels. The derived inflammatory indices further demonstrated clear differences between outcome groups, as NLR and SII were significantly higher in non-survivors, whereas HALP scores were significantly lower. In ROC analysis, NLR showed the strongest discriminatory ability for mortality (AUC = 0.80, 95% CI 0.74-0.85), followed by SII (AUC = 0.76, 95% CI 0.71-0.81) and HALP (AUC = 0.76, 95% CI 0.70-0.81). The optimal cutoff values were 4.26 for NLR, 958 for SII, and 2.15 for HALP. No significant correlations were identified between age and any of the three indices. Upon applying multivariable regression analysis, only NLR maintained its prognostic ability for ARDS-related mortality. Conclusions: Routine hematological parameters, together with derived inflammatory and nutritional indices, were significantly associated with mortality in patients with ARDS. Among the evaluated markers, NLR demonstrated the strongest prognostic performance, both in univariate and multivariate analysis, followed by SII and HALP. As these indices are derived from inexpensive, readily available laboratory tests, they may offer practical value for early risk stratification and clinical decision-making, particularly in resource-limited settings.