Barzilai University Medical Center

35 Research Day 2020 Barzilai University Medical Center 20 FACTORS RELATED TO OMALIZUMAB RESISTANCE IN CHRONIC SPONTANEOUS URTICARIA Magen E 1,3,4 , Chikovani T 2 , Waitman DA 3 , Kahan NR 3 . 1 Medicine C Department, Clinical Immunology and Allergy Division, Barzilai University Medical Center 2 Department of Immunology, Tbilisi State Medical University, Tbilisi, Georgia. 3 Leumit Health Services, Tel Aviv, Israel. 4 Faculty of Health Studies, Ben Gurion University of the Negev, Beer Sheva, Israel Background Omalizumab resistance (OmR) in chronic spontaneous urticaria (CSU) remains poorly understood. Objective To identify clinical and laboratory attributes of patients that may be predictive of OmR in CSU. Methods We conducted a retrospective observational study by using an electronic patient record data base of patients with severe CSU refractory to a fourfold H1-antihistamine dose, treated with omalizumab 300 mg every 4 weeks for at least 24 weeks. Complete response (CR) was defined as the reduction of baseline urticaria activity score by ≥ 90%, partial response (PR) by ≥ 30% to <90%, and OmR by <30% at 24 weeks. The patient characteristics of the CR, PR, and OmR groups were compared. Results Sixty-three patients (58.9%) had a complete remission at 24 weeks of omalizumab therapy, and 16 patients (14.9%) had OmR. The patients who were OmR were characterized by a higher rate of arterial hypertension 7 (43.8%), higher mean ± standard deviation (SD) high-sensitivity C-reactive protein (hs-CRP) level (10.3 ± 8.2 mg/L), mean ± SD white blood cell (WBC) count (9.1 ± 2.8 × 10³ cells/mL), and higher mean ± SD C3 level (164.3 ± 45.4 mg/dL) at baseline than the patients with CR (arterial hypertension, 9 [13.1%], p = 0.009; mean ± SD hs-CRP, 3.4 ± 10.1, p = 0.014; mean ± SD WBC count, 6.5 ± 3.8 × 10³ cells/mL, p = 0.012; and mean ± SD C3 level, 121.8 ± 42.1 m/dL, p < 0.001). In multivariable analysis adjusted for age, sex, and body mass index, OmR was associated with an hs-CRP level of >3.0 mg/L (odds ratio 1.94 [95% confidence interval, 1.28-3.15], p = 0.009) and with C3 > 160 mg/dL (odds ratio 1.54 [95% confidence interval, 1.05-2.36], p = .017). Conclusion Obesity, arterial hypertension, high plasma C3 level, and high-CRP level were associated with OmR in severe CSU.