Study Identifies Benefit to Using Basophil Release Assay for Chronic Spontaneous Urticaria Patients


This new data indicated that BHRA positivity could potentially be implemented as an omalizumab response predictor and showed the potential for off-label use.

Katrine Baumann, MSc, PhD

Credit: University of Copenhagen

Katrine Baumann, MSc, PhD

Credit: University of Copenhagen

Basophil histamine release assay (BHRA) positivity may be used as a predictor of poorer response to omalizumab for patients with type IIb chronic spontaneous urticaria (CSU), according to new findings, suggesting a need for off-label utilization.1

This research was highlighted in a recent letter to the editor exploring the use of BHRA—previously referred to as the HR-urticaria test—which is known to be valuable in distinguishing those with type IIb CSU.

Prior studies have shown that such patients have tended to report more severe CSU symptoms, have a generally less favorable outlook, and to exhibit greater resistance to second-generation antihistamines and omalizumab.2,3 Furthermore, those with type IIb autoimmune CSU represent a subgroup and clinical parameters often will not work to identify those with this condition.

These conclusions further highlighted the importance of this research, which was led by Katrine Baumann, MSc, PhD, from the Urticaria Center of Reference and Excellence (UCARE) at Bispebjerg Hospital’s Department of Dermato-Venereology & Wound Healing Centre in Copenhagen, Denmark.4

“To further characterize subgroups of CSU patients and to investigate the use of BHRA as a predictor of treatment response to omalizumab, we examined consecutive, newly referred, adult patients with CSU from a Urticaria Center of Reference and Excellence (UCARE) at a dermatological university hospital department (Bispebjerg Hospital, Copenhagen, Denmark),” Baumann and colleagues wrote.

Background and Findings

The investigators collected information on clinical characteristics, demographic data, patients’ comorbidities, details regarding treatment, patient-reported outcomes, and the duration of omalizumab utilization through the use of both interviews and clinical examinations.

They noted that BHRA results were viewed to be positive when patients’ basophil activation was shown to have exceeded 16.5%. The research team implemented IBM SPSS statistics v. 25 in order to assess their data.

The investigators added that continuous data were presented as means along with their standard deviations. Additionally, they used medians and ranges for continuous data and expressed the categorical data as percentages and numbers.

The team analyzed the link between patient-specific elements and BHRA test values using Spearman's rank correlation. They sought to explore connections between patient-specific factors and positivity of BHRA, utilizing both t-tests and Chi-square tests.

The investigators also did a receiver operating characteristics (ROC) analysis of the condition’s biomarkers to assess the area under the curve (AUC) value, specificity, sensitivity, and predictive values for positivity of BHRA. They also estimated the survival of omalizumab in relation to BHRA positivity, with the statistical significance of the p-value being less than 0.05.

Overall, the research team assessed a total of 385 subjects, comprising 279 women and 106 men, and they all had an average age of 40.5 years (ranging from 18 - 91 years). Among these individuals 13.8% were shown to have tested positive in the BHRA, with a higher prevalence among women with 16.1% compared to men with 7.5%.

The team further reported that when considering only pure CSU patients—with an exclusion for those with concomitant chronic inducible urticaria—the prevalence of the subjects’ BHRA positivity was found to be 16.0%, with a higher prevalence in women at 18.3% versus men with 9.6%. The data on BHRA-positive subjects also indicated that the median BHRA value was 46.1%.

Among the 385 individuals, 58.7% had been given treatment with omalizumab. In the others without, the investigators found that 56.3% of BHRA-positive ones and 26.0% of BHRA-negative ones discontinued the drug as a result of several different reasons in the initial year of treatment. This led to a substantial HR of 2.61 (P = .0003), and this remained statistically significant even following adjustment for several factors.

The investigators also added that other parameters, such as eosinophil count, were shown to have been able to predict a non-response to licensed-dosed treatment with omalizumab, adding that there was an HR of 3.37 (P < .001). Their analysis of ROC showed that total IgE, basophil number, and IgG-anti-TPO were helpful diagnostic markers in the identification of those with CSU and a positive BHRA, with AUC values of 0.87, 0.75, and 0.74, respectively.

These results by the investigators indicate that the biomarkers can effectively distinguish patients with positive BHRA results from those with negative results.

“Furthermore, in patients with BHRA positivity, a high prevalence of angioedema and thyroid disease was seen," they wrote. "This suggests that BHRA-positive patients may represent a distinct endotype of CSU."


  1. Baumann, K., Jørgensen, A.-H.R., Sørensen, J.A., Zhang, D.G., Ghazanfar, M.N., Skov, P.S., Woetmann, A., Vestergaard, C., Maurer, M. and Thomsen, S.F. (2023), Positive basophil histamine release assay predicts insufficient response to standard-dosed omalizumab in patients with chronic spontaneous urticaria. Clin Exp Allergy.
  2. Kolkhir P, Muñoz M, Asero R, et al. Autoimmune chronic spontaneous urticaria. J Allergy Clin Immunol. 2022; 149(6): 1819-1831.
  3. Marcelino J, Baumann K, Skov PS, et al. What basophil testing tells us about CSU patients – results of the CORSA study. Front Immunol. 2021; 12:742470.
  4. Schoepke N, Asero R, Ellrich A, et al. Biomarkers and clinical characteristics of autoimmune chronic spontaneous urticaria: results of the PURIST study. Allergy. 2019; 74(12): 2427-2436.
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