Association between circulating thyroperoxidase (TPO), anti-TPO IgE, anti-TPO IgG, and different clinical outcomes in chronic urticaria: A hypothesis-generating study

Background: In chronic spontaneous urticaria (CSU), multiple biomarkers have been described, including autoantibodies against thyroperoxidase (TPO). However, the simultaneous analysis of both IgE anti-TPO and IgG anti-TPO alongside blood TPO has not been performed. Objective: We conducted this hypothesis-generating study to evaluate the association between blood TPO, anti-TPO IgE, and anti-TPO IgG and explore their relationships with some clinical variables. Methods: Patients aged 12–80 years with a clinical diagnosis of CSU were included in this study. First, the biomarkers between a CSU group and a non-CSU group were compared (case–control design). Second, the relationship between the biomarkers and clinical characteristics was explored in the CSU group with a twelve-month follow-up. Results: The blood concentration of TPO was higher in the CSU group than in the control group, though this was not statistically significant (median 3.8 ng/mL vs. 13.3 ng/mL p = 0.4). The blood concentration of TPO was not associated with the presence of anti-TPO IgE or IgG. A total of 42 patients (61.2% versus 9.3% in non-CSU group) had anti-TPO IgG (29.4%) or anti-TPO IgE (42.6%) autoantibodies, and 7 patients (10.2%) had both. In the exploratory analysis, anti-TPO IgE and anti-TPO IgG were associated with different clinical clusters. Conclusion: In this hypothesis-generating study, TPO levels do not appear to determine the presence of autoantibodies in patients with CSU. About half of patients with CSU have either an IgE or IgG autoantibody against TPO, but few patients have both, and each autoantibody is associated with a different clinical profile, suggesting that there are perhaps independent CSU mechanisms with a common target. Future studies are required to confirm this hypothesis.