Baseline Monocyte Count Predicts Complete Response to Omalizumab in Chronic Spontaneous Urticaria: A Retrospective Analysis

TL;DR

Higher baseline monocyte counts may predict better response to omalizumab treatment in patients with chronic spontaneous urticaria.

Contribution

Baseline monocyte count is identified as a novel independent predictor of complete response to omalizumab in CSU.

Findings

11 out of 52 patients achieved complete response to omalizumab at week 12.

Complete responders had significantly higher baseline monocyte counts and lower CRP levels.

Omalizumab reduced neutrophil and monocyte counts specifically in responders.

Abstract

Introduction: Chronic spontaneous urticaria (CSU) is a distressing skin condition characterized by wheals and angioedema. While omalizumab is an effective biologic therapy for antihistamine-refractory CSU, a subset of patients shows partial or no response. Identifying reliable biomarkers to predict treatment outcomes remains a significant clinical need. This study aimed to investigate the relationship between systemic inflammatory parameters, specifically monocyte counts, and the clinical response to omalizumab.

Methods: This retrospective study included 52 patients with CSU treated with omalizumab (300 mg/four weeks) for at least 12 weeks at a tertiary referral center. Patients were stratified into two groups based on their response at week 12: "Complete Response" (Urticaria Activity Score over seven days (UAS7) = 0) and "Non-Complete Response." Baseline and post-treatment complete blood count (CBC) parameters, C-reactive protein (CRP), and total IgE levels were analyzed. Binary logistic regression was performed to identify independent predictors of response.

Results: Eleven patients (21.15%) achieved a complete response. The complete responder group exhibited significantly higher baseline median monocyte counts (0.68 vs. 0.40 K/µL, p = 0.001) and basophil counts (p = 0.032), but significantly lower baseline CRP levels (p = 0.003) compared to non-responders. Binary logistic regression analysis identified baseline monocyte count as the sole independent predictor of complete response (p = 0.036). Additionally, omalizumab treatment resulted in a significant reduction in neutrophil and monocyte counts, specifically in the responder group.

Conclusion: Higher baseline monocyte counts, alongside preserved basophils and low CRP levels, may define a distinct "responder clinical profile" (aligning with type I autoallergic CSU) that benefits maximally from omalizumab. Our findings suggest that higher baseline monocyte counts may serve as a potential independent predictor for complete treatment response.