Navigating the Haematological Maze: Unraveling the Role of NLR and PLR as Predictors of Dengue Severity- A Cross-sectional Study from Southern India

Abstract

Introduction: Dengue Fever (DF) poses a critical public health threat in tropical regions, displaying a spectrum of manifestations without distinct diagnostic hallmarks. Neutrophil to Lymphocyte Ratio (NLR) and Platelet to Lymphocyte Ratio (PLR) are useful biomarkers of inflammation and prognostic markers in various diseases. The inflammation that occurs in dengue is due to the exaggerated response of the immune system. Aim: To assess the utility value of NLR and PLR as prognostic markers for dengue severity. Materials and Methods: A cross-sectional study was conducted on 99 admitted Dengue patients. Patients were grouped into three categories: DF, Dengue Haemorrhagic Fever (DHF), and Dengue Shock Syndrome (DSS). Various parameters of Complete Blood Count (CBC), NLR, and PLR were compared among the groups using Analysis of Variance (ANOVA) test (p-value <0.05 considered significant). Sensitivity, specificity, and accuracy were calculated using Receiver Operating Characteristic (ROC) curve. Results: Among the 99 patients, 63.6% exhibited thrombocytopenia (platelet count <1.5 lac/dL), and 7% of patients had a platelet count <20,000/dL. All DHF and DSS patients had thrombocytopenia. Leucopenia was evident in 45.45% of patients, with 6% having a Total Leukocyte Count (TLC) <2000/dL. TLC remained stable across these stages. The mean NLR in DF was 2.47 (range 0.1-15.4), in DHF it was 1.013 (range 0.2-3.2), and in DSS it was 0.41 (range 0.08- 0.65.17) with a p-value of 0.02. The PLR displayed substantial differences, with mean values of 134.4 (range 10.1-273.8) for DF, 50.57 (range 7.1-96.1) for DHF, and 10.39 (range 3.1-38.8) for DSS with a p-value of 0.003. NLR had 63% accuracy, 77.8% sensitivity, and 94.4% specificity. PLR had 81.5% accuracy, 93.3% sensitivity and 33.3% specificity. Conclusion: The specificity of NLR was higher, while PLR exhibited superior accuracy and sensitivity in detecting severe cases.