Single-center retrospective study associates ferritin and eosinophil levels with acute asthma exacerbation in children

Vitamin D and iron metabolism are increasingly recognized as potential modulators of airway inflammation, yet their interrelationship in pediatric asthma remains unclear. This study investigated the associations of serum vitamin D, ferritin, and eosinophilic inflammation with acute asthma exacerbations in children and explored their potential interaction. This single-center retrospective study included 120 children with asthma, comprising 60 with acute exacerbation and 60 in clinical remission. Serum 25-hydroxyvitamin D [25(OH)D], ferritin, interleukin-6 (IL-6), and eosinophil-related indices were measured. Group comparisons, Spearman correlation analysis, univariate and multivariable logistic regression, restricted cubic spline analysis, and decision curve analysis were performed. Compared with the remission group, children with acute exacerbation had significantly higher ferritin levels (median 145 vs. 82 ng/mL, P < 0.001) and eosinophil percentage (6.0% vs. 4.7%, P < 0.001), but lower vitamin D levels (18.6 ± 7.2 vs. 24.3 ± 8.7 ng/mL, P = 0.021). In multivariable logistic regression, ferritin (OR = 1.13, 95% CI 1.07–1.18) and eosinophil percentage (OR = 2.01, 95% CI 1.34–2.70) remained independently associated with acute exacerbation, whereas vitamin D was not statistically significant after adjustment, although the association remained directionally inverse (OR = 0.92, 95% CI 0.84–1.02). No significant interaction between ferritin and vitamin D was observed, but interaction testing was limited by sample size. Restricted cubic spline analysis suggested an inverse linear association between vitamin D level and exacerbation risk. The combined model including ferritin, eosinophil percentage, and vitamin D showed high apparent discrimination (AUC = 0.973, 95% CI 0.952–0.994), although this finding should be interpreted cautiously because of overfitting risk. Ferritin and eosinophil percentage were independent risk factors for acute asthma exacerbation in children. Vitamin D showed an inverse association in unadjusted and dose-response analyses but was not an independent predictor after multivariable adjustment. These findings support a possible link between metabolic and inflammatory pathways in childhood asthma, but larger studies are needed for validation.