Background: About 25-45% of patients of chronic urticaria (CU) have been stated to have histamine releasing autoantibodies in their blood. The term autoimmune urticaria is increasingly being accepted for this subgroup of patients. Review of the literature suggests high autologous serum skin test (ASST) positivity and presence of antithyroid microsomal antibodies in patients with autoimmune urticaria.
Aims: To study prevalence of ASST positivity and antithyroid microsomal antibodies in chronic "idiopathic" urticaria and to study the correlation between the two parameters.
Methods: All patients of chronic idiopathic urticaria satisfying inclusion/exclusion criteria were enrolled in the study after written informed consent. Patients of CU secondary to infections and infestations, physical urticaria including dermatographism, mastocytosis, urticarial vasculitis and those on treatment with immunosuppressive drugs for urticaria were excluded from the study. In all of these patients, complete blood count; ASST, serum T3/T4/thyroid stimulating hormone levels, antithyroid microsomal antibody (AMA) levels were done. Statistical analysis was done by Chi-square test, Fisher exact test and Kappa statistics.
Results: Study included 24 males and 26 females with mean age of 39.54 years. Majority of patients belonged to 20-40 years of age. Females showed more ASST positivity. A total of 12 out of 50 (24%) patients showed positive ASST. A total of four out of 12 (33.33%) had positive ASST and raised AMA levels.
Conclusion: Only 25% of patients of chronic idiopathic urticaria had positive ASST. ASST and AMA levels were positively correlated in our study. Further studies are required to authenticate this association.
Keywords: Autologous serum skin test; antithyroid microsomal antibody; chronic autoimmune urticaria; chronic urticaria.