Real-world treatment patterns and healthcare utilization following omalizumab initiation in chronic spontaneous urticaria: a nationwide Brazilian cohort study

Chronic spontaneous urticaria (CSU) is a relapsing inflammatory skin disease associated with substantial symptom burden and repeated healthcare use. Omalizumab is recommended for patients whose disease remains uncontrolled despite second-generation H1-antihistamines, yet large-scale data describing its use in routine care remain limited, particularly in Latin America. The objective of this study is to characterize patients initiating omalizumab for CSU in a large Brazilian healthcare system and examine treatment patterns, healthcare utilization, and concomitant medication use before and after treatment initiation. We conducted a population-based retrospective cohort study using the institutional data lake of a nationwide integrated healthcare organization covering more than 8.9 million beneficiaries. Patients with CSU initiating omalizumab between January 2020 and December 2025 were identified from administrative authorization records linked to clinical and healthcare utilization data. The index date was the first administrative authorization for omalizumab. The primary longitudinal analysis compared healthcare utilization during the 12 months before and after the index date. Omalizumab dosing patterns, treatment exposure, concomitant medication use, and changes in healthcare utilization were assessed. Negative binomial regression was used in sensitivity analyses to estimate incidence rate ratios. The cohort included 492 patients; the mean age was 41.3 ± 13.5 years and 394 (80.1%) were women. Among 472 patients with available dosing information, 4614 omalizumab administrations were recorded, with doses ranging from 150 to 600 mg and a median of nine treatment cycles per patient. In the 12-month paired analysis (n = 429), mean outpatient visits increased from 5.10 to 10.31 per patient after treatment initiation (p < 0.001; IRR, 2.021; p < 0.001). Emergency department use did not change significantly (2.71 vs 2.45 visits per patient; p = 0.291; IRR, 0.907; p = 0.191), nor did hospitalizations (0.07 vs 0.08 per patient; p = 0.816; IRR, 1.065; p = 0.797). Recorded concomitant prescriptions declined from 541 in the pre-index period to 193 in the post-index period. Among patients evaluable for the guideline-concordance analysis, 95.1% were not receiving chronic treatment classified as non-recommended by the study definition. In this nationwide cohort from a Brazilian integrated healthcare system, omalizumab initiation coincided with a change in the pattern of recorded healthcare use for CSU: outpatient contacts increased substantially, whereas emergency department visits and hospitalizations remained statistically stable, and recorded concomitant prescribing declined. Because the study was observational and relied on administrative data without validated measures of disease activity or a concurrent comparator group, these findings describe patterns of care within this healthcare system rather than the clinical effectiveness of omalizumab or its causal impact on healthcare utilization, and extrapolation beyond the Brazilian supplementary healthcare setting studied here should be made with caution.