Ferritin-to-Zinc Ratio, Treatment Escalation, and Weight-for-Age Improvement in Children with Atopic Dermatitis: A Retrospective Cohort Study

Background/Objectives: Ferritin and zinc are influenced by nutritional and inflammatory status. The longitudinal relevance of the ferritin-to-zinc ratio (FZR) in pediatric atopic dermatitis (AD) is unclear. We examined whether baseline FZR was associated with 6-month treatment escalation and weight-for-age improvement. Methods: This retrospective study included 297 children aged ≤10 years with AD and an independent same-center replication cohort of 211 children. FZR was analyzed per 0.5-unit increase and by derivation-defined strata. Models adjusted for age, sex, baseline Eczema Area and Severity Index (EASI) score, weight-for-age Z-score (WAZ), and C-reactive protein (CRP). Weight-for-age improvement was defined as a ≥0.5 increase in WAZ. Results: Treatment escalation occurred in 71 children, and weight-for-age improvement occurred in 134. Higher FZR was associated with treatment escalation (adjusted odds ratio (aOR) 2.05, 95% confidence interval (CI) 1.38–3.04) and lower odds of weight-for-age improvement (aOR 0.55, 95% CI 0.38–0.79). Optimism-corrected area under the receiver operating characteristic curve (AUC) increased from 0.691 to 0.770 and from 0.642 to 0.722, respectively. Associations were replicated for treatment escalation (aOR 1.78, 95% CI 1.20–2.65) and weight-for-age improvement (aOR 0.63, 95% CI 0.44–0.90). Conclusions: Baseline FZR was associated with both outcomes but may partly reflect inflammatory disease burden; prospective evaluation is needed before clinical application.