What Basophil Testing Tells Us About CSU Patients – Results of the CORSA Study

Chronic spontaneous urticaria (CSU) is a common condition in adults and children, impacting the quality of life. Recent studies characterized chronic spontaneous urticaria as an autoantibody-driven condition, with mast cells and basophils being activated through two distinct pathways: type I autoimmune CSU, where IgE autoantibodies are cross-linked by self-antigens; and type IIb autoimmune CSU, where IgG and IgM autoantibodies are directed against IgE receptors on the surface of mast cells and basophils. Basophil testing is the most effective way to diagnose type IIb autoimmune CSU: a positive basophil test correlates to long disease duration, higher disease activity, poor response to antihistamines and omalizumab, and a better response to cyclosporine and fenebrutinib.

The objective of this study was to identify features of basophil test-positive patients.

This was a cross-sectional study that included 85 participants with CSU. They were tested for basophils with the basophil-activation test (BAT), the basophil histamine release assay (BHRA), and data were statistically analyzed.

Of all the participants, 44% tested positive with the BAST, and 28% tested positive with BHRA. These participants had higher activity and impact of disease, less disease control, and lower total serum IgE. In contrast, they had a higher rate of positive autologous serum skin test (ASST), angioedema, nocturnal symptoms, symptoms more than five days/week, and thyroid autoantibodies. The ASST was a good predictor of a positive basophil test when combined with angioedema, thyroid autoantibodies, and low IgE.

This study showed that a positive basophil test is related to known characteristics of type II autoimmune CSU, allowing a better approach to these patients’ condition management.