Neutrophil-to-Lymphocyte ratio (NLR), Monocyte-to-Lymphocyte ratio (MLR), Platelet-to-Lymphocyte Ratio (PLR) and Red Cell Distribution Width (RDW) to predict outcome and differentiate between viral and bacterial pneumonia in the intensive care unit: a retrospective study

Abstract Purpose Neutrophil-to-Lymphocyte ratio (NLR), Monocyte-to-Lymphocyte ratio (MLR), Platelet-to-Lymphocyte Ratio (PLR), and Red Cell Distribution Width (RDW) are emerging biomarkers to predict outcome in general ward patients. However, their role in the prognostication of critically ill patients with pneumonia is unclear. Material and Methods 216 adult patients were enrolled over 2 years. They were classified into viral and bacterial pneumonia groups, represented by influenza A virus and Streptococcus pneumoniae, respectively. Demographics, outcomes, and laboratory parameters were analysed. The prognostic power of blood parameters was determined by their respective area under the receiver operating characteristic curve (AUROC). Their performance was compared with the APACHE IV score. Discriminant ability in differentiating viral and bacterial aetiologies was studied. Results Viral and bacterial pneumonia were identified in 111 and 105 patients, respectively. In predicting hospital mortality, the APACHE IV score was the best prognostic score compared with all the studied blood parameters (AUC 0.769, 95% CI 0.705-0.833). In classification tree analysis, the most significant predictor of hospital mortality was the APACHE IV score (adjusted P=0.000, χ2 = 35.591). Mechanical ventilation was associated with higher hospital mortality in those patients with low APACHE IV score <=70 (adjusted P=0.014, χ2 = 5.999). In patients with high APACHE IV score >90, age (>78, adjusted P=0.007, χ2 = 11.221) and thrombocytopenia (platelet count <=128, adjusted P=0.004, χ2 = 12.316) were predictive of higher hospital mortality. Conclusion Novel inflammatory biomarkers were not comparable to the APACHE IV score in predicting hospital mortality. In differentiation between viral and bacterial pneumonia, there is no ideal biomarker.