Neutrophil-to-lymphocyte ratio as a biomarker for asthma identification and severity stratification: a systematic...

Reliable biomarkers for asthma identification and severity stratification remain lacking. The neutrophil-to-lymphocyte ratio (NLR) has emerged as a potential candidate, but evidence remains inconsistent. This study evaluates the value of NLR in distinguishing asthma patients from healthy controls and its correlation with disease severity.

A systematically search was conducted across PubMed, Embase and Web of Science for studies reporting NLR levels in asthma patients and healthy controls. Pooled mean differences (MD) and 95% confidence intervals (CIs) were calculated using random-effects models. Receiver operating characteristic (ROC) curves assessed discriminative performance.

Nineteen studies (43,164 patients, 8,411 controls) were included. When comparing across different asthma severities, the NLR showed incremental increases across severity: mild vs. moderate asthma (MD = -0.41, 95% CI: -0.64 to -0.18, p = 0.0005), mild vs. severe (MD = -3.10, 95% CI: -6.26 to 0.06, p = 0.05), and moderate asthma vs. severe asthma (MD = -2.44, 95% CI: -5.31 to 0.44, p = 0.10). The comparison between severe and non-severe asthma also showed a significant difference (MD = -2.06, p < 0.0001). NLR robustly discriminated asthma from controls (AUC = 0.929) and severe from non-severe asthma (AUC = 0.914). Subgroup analyses revealed higher NLR differences in pediatric populations and developed regions.

NLR is a promising biomarker for asthma and severity stratification, although its discriminative ability between moderate and severe stages is limited. Future studies should explore its role in predicting asthma progression and exacerbations.