Basophil activation test in chronic spontaneous urticaria

Chronic spontaneous urticaria (CSU) is a condition in children characterized by a potentially complex etiology and a significant impact on quality of life. The objective of this study was to evaluate the clinical utility of the indirect Basophil Activation Test (BAT), an in vitro method, in pediatric CSU patients and to investigate the association of test results with the Autologous Serum Skin Test (ASST), disease activity (UAS7), and hematological inflammation parameters (NLR, PLR, SII, SIRI, PIV). The study included 30 pediatric patients (aged 0-18 years) diagnosed with chronic spontaneous urticaria who presented to the Department of Pediatric Allergy and Immunology at Akdeniz University Faculty of Medicine between August 2022 and January 2025. Indirect BAT and ASST were performed on the patients; disease severity was assessed using the Urticaria Activity Score 7 (UAS7), and inflammation indices were calculated from complete blood count parameters. Indirect BAT results were obtained by measuring surface activation markers, such as CD63 and CD203c, via flow cytometry following the incubation of patient sera with basophils obtained from a healthy donor. In the study cohort, BAT positivity was found to be 16.7%, and ASST positivity was 10%. When comparing BAT-positive and BAT-negative groups, UAS7 scores (p=0.022) and SIRI levels (p=0.038) were found to be statistically significantly higher in BAT-positive individuals. Furthermore, when stratified based on the median BAT value (2.3%) of the entire cohort, the group exhibiting "high reactivity" (≥2.3%) demonstrated significantly elevated levels of CRP (p=0.008), C3 (p=0.033), NLR (p=0.042), PLR (p=0.024), and SII (p=0.046). Our study indicates that indirect BAT positivity in pediatric CSU is associated with more severe disease activity and an increased systemic inflammatory burden. BAT holds potential as a more objective marker compared to ASST, particularly in identifying the autoimmune subtype. However, further multicenter studies involving larger patient cohorts are required to definitively establish the diagnostic and prognostic value of these parameters.