# 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.

## Key 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.