Association of peripheral blood lymphocytes and immunoglobulins with disease severity in pediatric acute respiratory distress syndrome: an age-stratified retrospective study

Pediatric acute respiratory distress syndrome (PARDS) carries significant morbidity and mortality. Identifying immune biomarkers associated with disease severity could enhance risk stratification. This study investigated the association of peripheral lymphocytes and immunoglobulin levels with PARDS severity across different pediatric age groups. A retrospective analysis was conducted on 486 children (aged 28 days to 14 years) with PARDS admitted to Hebei Children’s Hospital between January 2019 to May 2024. Patients were stratified by age (four groups) and disease severity (mild/moderate vs. severe per PALICC-2 criteria). Demographic, clinical, and laboratory data were obtained from medical records, including peripheral lymphocyte subsets and immunoglobulin (IgA, IgG, IgM) levels measured within 48 h of admission. Feature selection was performed using Least Absolute Shrinkage and Selection Operator regression, followed by multivariable logistic regression to identify severity-associated factors. Predictive performance for disease severity was assessed via receiver operating characteristic (ROC) curve analysis, with area under the curve (AUC). Lymphocyte counts were significantly lower in severe versus mild/moderate PARDS across all age groups (p < 0.05). While most immunoglobulin levels did not vary significantly by severity, IgA levels were significantly lower in the severe group among children aged 7–14 years (P < 0.05), a nuance not observed in younger cohorts. LASSO-selected, age-specific predictors included total T lymphocyte count (infants), and both total T lymphocyte proportion and count plus total B lymphocyte proportion (older children). In the 28 days–1 year group, total T lymphocyte count predicted severe PARDS (AUC = 0.901, 95% CI 0.837–0.964). In the 7–14-year group, total T lymphocyte proportion, total B lymphocyte proportion, and total T lymphocyte count were significant predictors (AUCs = 0.926, 0.895, and 0.702, respectively; all p < 0.05). Peripheral lymphocyte subsets, but not immunoglobulin levels, are significantly associated with PARDS severity and demonstrate age-specific predictive patterns. Lymphocyte profiling at admission may offer clinical utility for identifying severe cases and reflect the underlying immune dysregulation in PARDS.