Autologous serum skin test in chronic spontaneous urticaria: Evaluation of the relationship with disease activity and autoimmune antibodies.

Introduction: Chronic spontaneous urticaria (CSU) is a multifactorial, mast cell driven disorder characterized by wheals, angioedema, or both, lasting for more than six weeks. Autoimmunity, particularly Type IIb autoimmunity, involving IgG autoantibodies directed against either IgE or its high affinity receptor (FcεRI) on mast cells and basophils, plays a significant role in CSU pathogenesis. The Autologous Serum Skin Test (ASST) is a practical tool for detecting IgG autoantibodies and may be associated with the disease severity and the presences of autoimmune antibodies. Nonetheless, previous studies on ASST responses and the clinical features of patients with CSU have conflicting results.

Materials and methods: This study aimed to establish the relationship between ASST positivity and disease activity, assessed by the Urticaria Activity Score 7 (UAS7) and to determine the associations with autoimmune antibodies including anti-thyroid peroxidase (anti-TPO), antithyroglobulin antibodies, and antinuclear antibodies (ANA). This cross- sectional study was conducted over a five months period, from January to May 2024, at the Department of Dermatology, in the tertiary hospital located in the capital city of Malaysia. Participants underwent ASST, laboratory evaluation for autoimmune antibodies, and assessment of disease activity using UAS7.

Results: In this study, 24 of the 59 patients were ASST positive, resulting in a prevalence rate of 41%. ASST positive patients demonstrated significantly higher disease activity, with a mean UAS7 score of 23.96 ± 10.55, compared to 13.51 ± 10.88 in ASST negative individuals (p = 0.001). A significant association was also found between ASST positivity and higher UAS7 severity categories (p = 0.011). Furthermore, a significant gender difference was observed with females more likely to exhibit ASST positivity (p = 0.016). Nevertheless, no significant associations were found between ASST results and presence of angioedema (p =1.0), atopy (p = 0.968), or autoimmune antibodies including ANA, anti-TPO, and anti-thyroglobulin antibodies (p > 0.05) CONCLUSION: The significant association between ASST positivity and increased UAS7 scores heightened interplay between autoimmunity, disease severity, and clinical characteristics in CSU, particularly Type IIb autoimmunity subtype. Hence, ASST is a practical clinical tool for identifying autoimmune profile in CSU patients, and aids dermatologist in prognosis assessment and treatment strategies.