Eosinophilic cationic protein and D-Dimer are potential biomarkers to predict response to antihistamines but not to omalizumab in chronic spontaneous urticaria.

Introduction: Biomarkers that could reliably anticipate the effectiveness of antihistamines and omalizumab in treating chronic spontaneous urticaria (CSU) have not been conclusively identified. Our objective was to examine how eosinophilic cationic protein (ECP), tryptase, D-dimer, and total Immunoglobulin E (IgE) impact the response to antihistamine and omalizumab treatments in individuals with CSU.

Methods: In this cross-sectional retrospective study, CSU patients that had undergone treatment with either antihistamines or omalizumab for a minimum of 12 weeks between 2015 and 2021 at an Allergy and Immunology Department were analyzed. Several demographic and laboratory parameters including eosinophil counts, mean platelet volüme (MPV), sedimentation, C-reactive protein (CRP), antinuclear antibodies (ANA) and Anti-thyroperoxidase (Anti-TPO) and total IgE, tryptase, ECP and D-dimer were retrived from patient files. The association of these biomarkers with Urticaria Control Test (UCT) and the effect of these biomarkers on treatment response were evaluated. Treatment response was assessed using the UCT, with a score of UCT ≥ 12 indicating a responder and UCT < 12 indicating a non responder.

Results: The patients in the omalizumab group were older, had a longer disease duration and had worse urticaria control (lower baseline UCT scores). 421 patients were treated with antihistamines and 88 patients were treated with omalizumab. ECP was found to be inversely correlated with baseline UCT (p < 0.001 r=-0.268). ECP and D-dimer levels of non-responder patients in the antihistamine group were significantly higher than in responder patients (ECP: 49 ng/mL vs 28.1 ng/mL, p < 0.001) (D-dimer: 0.60 mg/L vs 0.30 mg/L, p < 0.001), while there were no significant difference in terms of tryptase and total IgE. These four biomarkers were similar, in omalizumab responders and non responders.

Conclusion: In this study with CSU, we looked at predictors of responses to treatments. ECP can serve as a marker of poor urticaria control and may predict antihistamine refractoriness along with D-dimer.