D2.54 - Basophil Activation Test for Chronic Spontaneous Urticaria: the experience of a paediatric allergy centre

Chronic spontaneous urticaria (CSU) is a condition characterized by recurrent and transient itchy wheals and/or angioedema, lasting for at least six weeks and occurring on most days. The condition is frequently associated with autoimmune disorders. In addiction, it is estimated that up to 40% of CSU patients presents auto-antibodies that activate mast cells (MCs) and basophils by binding the FCεRI ( high-affinity IgE) receptor. In fact, type I (immunocomplexes autoantigen–IgE activating MCs) and/or type IIb (autoantibodies activating MCs, including anti-FcεRI and anti-IgE) autoimmune responses contribute to the pathogenesis of CSU. The former is associated to higher IgE levels and allergic diseases; the latter is linked to autoimmune disorders, lower IgE and worse clinical picture. Basophil Activation Test (BAT) can be used to detect autoimmune CSU subtype. It consists in a flow- cytometry essay that measures the expression of CD63 on heterologous peripheral blood basophils from donors,  which are activated by the serum of CSU patients, thereby reducing the need for in vivo testing.    

BAT was considered positive when the percentage of basophil activation was at least 5% and the stimulation index (the percentage of activated basophils after stimulation) was higher than 2% from at least one donor ( blood type 0).

BAT was conducted on 35 patients ( 16 males, 19 females) aged 1 -17 years, with a mean age of 9 years. It resulted positive in 22 patients (62%) of whom 13 (59%) showed allergic sensitization. A positive autoimmunity test was found in 20% of subjects. Furthermore, it was observed that 3 out of 5 patients with ANA positivity also had a positive BAT result. Finally, 2 of 3 patients diagnosed with autoimmune thyroiditis also demonstrated a positive BAT. 

BAT can provide valuable insight to identify spontaneous or autoimmune CSU, having good sensitivity and specificity. In addition, in literature, a positive BAT has been linked to longer duration and poor response to antihistamines or Omalizumab. However, further evidence, standardization and availability of the test are needed to guarantee a wider use in clinical paediatric practice.