Autoimmune chronic spontaneous urticaria (aiCSU) comes with high disease activity and poor response to treatment. Recently, elevated levels of IgG anti-thyroid peroxidase (aTPO) and low levels of total IgE were reported to be common in aiCSU.
Here, we investigated how high aTPO and low IgE individually and combined are linked to features of aiCSU, including treatment responses.
We analyzed records of CSU patients from two independent cohorts (n=1,120) for demographic, clinical, laboratory parameters and treatment responses. Total IgE and aTPO were measured, and four markers of aiCSU were analyzed: autologous serum skin test (ASST), basophil activation test (BAT), eosinophil and basophil numbers. Cut-off values were ≥34 kU/L (high aTPO) and <40 IU/mL (low total IgE).
One of ten CSU patients had both high aTPO and low IgE (aTPO↑IgE↓, 11%, n=123). aTPO↑IgE↓ was linked to higher age at CSU onset, being female, angioedema and shorter CSU duration. aTPO↑IgE↓ was associated with markers of aiCSU, i.e. BAT and ASST positivity, basopenia, and eosinopenia (p<0.01 for all). Almost half of the aTPO↑IgE↓ (44%, 19/43) patients had a positive BAT, the best single marker for aiCSU, versus 12% (43/344) of non-aTPO↑IgE↓ patients (p<0.001). Relative risk of showing BAT positivity for an aTPO↑IgE↓ patient is 3.636 (95% CI, 2.382 to 5.551). aTPO↑IgE↓ patients showed low response rates to antihistamine treatment as compared to non-aTPO↑IgE↓ (30 vs 47%, p=0.01).
Our findings suggest that aTPO↑IgE↓ is a useful diagnostic marker for aiCSU in everyday clinical practice.

Copyright © 2021. Published by Elsevier Inc.