Age-stratified correlations between atopic dermatitis severity and biomarkers: hypercoagulability as a key indicator of severity in older adults.

Background: Atopic dermatitis (AD) is a chronic skin disorder with systemic inflammation. Previous studies have focused primarily on its allergic characteristics, whereas the accompanying systemic inflammation and potential hypercoagulable state, particularly across different age groups, have received insufficient attention. Objective: To investigate the correlations between AD severity and systemic inflammation, hypercoagulability, and allergic responses, and to evaluate the age-specific predictive value of these biomarkers. Methods: This cross-sectional study enrolled 181 patients with AD and 101 healthy controls. Disease severity was assessed using the Eczema Area and Severity Index (EASI). Blood samples were analyzed for allergic markers (total IgE and absolute eosinophil count), coagulation markers [D-dimer (D-D), fibrinogen degradation products, and D-dimer-to-fibrinogen ratio [DFR]], and systemic inflammation indices [systemic immune-inflammation index (SII), platelet-to-lymphocyte ratio (PLR), neutrophil-to-lymphocyte ratio, monocyte-to-lymphocyte ratio, and systemic inflammation response index]. Participants were stratified by age (<60 vs. ≥ 60 years). Group comparisons were performed using non-parametric tests, correlations were assessed using Spearman analysis, and predictive performance was evaluated using receiver operating characteristic curves. Results: All measured biomarkers were significantly higher in patients with AD than in controls ( Conclusion: Patients with AD exhibit significant systemic inflammation, a subclinical hypercoagulable state, and enhanced allergic responses. Total IgE, SII, and PLR are reliable age-independent severity biomarkers. The diagnostic utility of coagulation markers and eosinophil counts is age-dependent. Based on these results, we suggest a practical, age-stratified clinical approach. In all patients with AD, total IgE, SII, and PLR were measured as core severity markers. In patients aged <60, DFR (AUC = 0.723) was used to distinguish mild-to-moderate disease. For those aged ≥60, D-dimer (AUC = 0.805) and the absolute eosinophil count were prioritized (AUC = 0.688) to predict moderate-to-severe AD. Monitoring systemic inflammation and coagulation is clinically relevant, particularly in elderly patients with moderate-to-severe AD.