Threshold effect of white blood cell count on the risk of refractory Mycoplasma pneumoniae pneumonia in pediatric patients: A retrospective cohort study

Refractory Mycoplasma pneumoniae pneumonia (RMPP) remains a major challenge in pediatric respiratory infections, with limited early predictors for disease progression. White blood cell (WBC) count is a widely used biomarker, but its relationship with RMPP risk has not been fully elucidated. This study investigates the threshold effect of WBC count on RMPP development to enhance risk stratification and early intervention strategies. A retrospective cohort study was conducted on pediatric patients diagnosed with MPP. WBC count was analyzed as both a continuous variable and stratified into quartiles to evaluate its association with RMPP risk using multivariable logistic regression. A threshold effect analysis was performed, and model selection was determined by the log-likelihood ratio test (P = .017). Adjustments were made for age, gender, weight, inflammatory markers (C-reactive protein, interleukin-6, γ-IFN), and metabolic indicators (lactate dehydrogenase, lactate, ALT, AST). A nonlinear relationship between WBC count and RMPP risk was identified. A threshold at WBC = 14.3 × 109/L was detected, which serves as a critical diagnostic indicator. When WBC count exceeds this threshold, it strongly suggests the development of RMPP. For WBC levels below 14.3 × 109/L, each 1 × 109/L increase was associated with a 20% higher RMPP risk (OR = 1.2, 95% CI: 1.1-1.2, P < .001), indicating that moderate WBC elevations are a strong predictor of disease progression. The WBC count was associated with the development of refractory RMPP. WBC count could be used as a crucial biomarker for risk stratification and clinical decision-making in pediatric MPP, providing clinicians with a clear threshold for early intervention and close monitoring.