Neutrophil-lymphocyte ratio as a point-of-care marker for predicting bacterial etiology in pediatric community-acquired Pneumonia: A comparative analysis with C -reactive protein

Abstract

Objectives

To evaluate the role of NLR in predicting bacterial etiology in pediatric community acquired pneumonia and compare its diagnostic performance with CRP.

Methods

This retrospective analytical study was conducted in a tertiary care center in South India. The clinico-laboratory data of children with pneumonia were reviewed. The diagnostic performance was evaluated using appropriate statistical methods.

Results

Among 514 children with community-acquired pneumonia, 398 were included. Bacterial pneumonia was diagnosed in 250 (62.8 %) children. The median NLR among children with bacterial pneumonia was 3.3 (2.18, 5.7) compared to 1.3 (0.685, 2.595) among children with non-bacterial pneumonia [p < 0.001]. A CRP cut-off value of 31.5 mg/L had a sensitivity of 85.2 % and a specificity of 93.2 %, respectively [AUC 0.923; 95 % CI (0.895, 0.952); p < 0.001]. The positive and negative predictive values of CRP to predict bacterial pneumonia were 95.52 % and 78.86 %, respectively, while the positive and negative likelihood ratios were 12.61 (6.92, 22.99) and 0.16 (0.12, 0.21), respectively. An NLR cut-off of 1.74 had a sensitivity of 87.6 % and a specificity of 62.8 %, respectively [AUC 0.78, 95 % CI (0.729, 0.831); p < 0.001]. The positive and negative predictive values of NLR to predict bacterial pneumonia were 79.93 % and 75 %, respectively, while the positive and negative likelihood ratios were 2.36 (1.90, 2.92) and 0.19 (0.14, 0.28), respectively. Bayesian reasoning on positive NLR shifted the post-test probability of bacterial pneumonia to 79.9 %.

Conclusion

NLR has moderate specificity and should be viewed primarily as a sensitive, accessible, and rapid screening or triage tool, especially useful in resource-limited settings.