Neutrophil-to-lymphocyte ratio for predicting disease severity and outcomes in children with Mycoplasma pneumoniae pneumonia: a systematic review and meta-analysis

To systematically evaluate the diagnostic and prognostic value of the neutrophil-to-lymphocyte ratio (NLR) in children with Mycoplasma pneumoniae pneumonia (MPP). A comprehensive search of PubMed, Embase, Web of Science, Cochrane Library, Scopus, Wanfang, and CNKI was performed from inception to November 1, 2025. Observational studies assessing the association between NLR and the occurrence of MPP, refractory MPP (RMPP), severe MPP (SMPP), or poor prognosis in children were included. Two reviewers independently screened the literature, extracted data, and assessed the risk of bias. Random-effects models were applied to pool odds ratios (OR) and standardized mean differences (SMD) with 95% confidence intervals (CI). Meta-regression analyses were conducted to explore potential sources of heterogeneity. Twenty-six studies involving 7,013 participants were included. Elevated NLR was significantly associated with the occurrence of MPP (6 studies, SMD = 1.91, 95% CI: 1.07–2.76), RMPP (5 studies, OR = 2.15, 95% CI: 1.44–3.21; 7 studies, SMD = 0.82, 95% CI: 0.64–1.00), SMPP (4 studies, OR = 1.41, 95% CI: 1.27–1.56; 9 studies, SMD = 1.36, 95% CI: 0.79–1.93), and poor prognosis (8 studies, OR = 1.55, 95% CI: 1.30–1.84; 10 studies, SMD = 1.13, 95% CI: 0.74–1.53). Meta-regression indicated that geographic region accounted for most heterogeneity in MPP analyses (R²= 70.0%), while sample size contributed substantially to heterogeneity in SMPP (R²= 51.2%) and adverse outcome analyses (R²= 60.5%). Sensitivity analyses confirmed the robustness of the findings. As an adjunct to clinical assessment and etiological testing, NLR shows potential as a supportive biomarker for the early risk stratification and prognosis monitoring of pediatric MPP. Substantial heterogeneity was observed across continuous analyses, and most included studies originated from East Asia, which may limit generalizability. Its simplicity and low cost suggest possible clinical utility, particularly in resource-limited settings.