Basophil activation test in children with autoimmune chronic spontaneous urticaria: Is it ready for clinical practice?

Introduction: Chronic spontaneous urticaria (CSU) is characterized by recurrent itchy wheals, angioedema or both, that persist for longer than six weeks. In children, up to 40% of chronic spontaneous urticaria is due to mast cells and basophils-activating autoantibodies, mostly directed against the IgE high-affinity receptor subunit (FcεRI). Indirect basophil activation test (BAT) has been proposed in the diagnosis of autoimmune urticaria.

Materials and methods: Sera from sixteen patients, aged from 2 to 15 yrs, with CSU were evaluated through indirect BAT by flow cytometry using a commercial kit (Flow CAST®, BUHLMANN Laboratories, Schonenbuch, Switzerland) according to the manufacturer's instructions.

Results: Indirect BAT test gave a much better diagnosis in our cohort than the gold standard ASST. Six children (37.5%) showed a positive indirect BAT while we could perform ASST in only 3 patients with just one patients showing a positive ASST. The specificity of BAT positive results was confirmed by the absence of significant difference between the BAT results obtained from negative controls vs negative sera of the patient (p = 0.65) on the basophil donors, indicating that the serum is not activating basophil per se.

Conclusions: This pilot study suggests the utility of BAT to identify the subtype of autoimmune CSU in children in clinical practice.