Circulating basophils in patients with type IIb autoimmune chronic spontaneous urticaria have a lower histamine content

Background: Patients suffering from chronic spontaneous urticaria (CSU) aretypically classified as type I or type IIb autoimmune CSU, but further patientstratification is hindered by the lack of biomarkers.Objectives: We investigated whether the histamine content of individualbasophils differ between patient subtypes in CSU to evaluate its potential as abiomarker.Methods: A total of 101 patients diagnosed with CSU were included in thestudy. The histamine content per circulating basophil was derived from thebasophil count in peripheral blood and levels of total cellular blood histamine.These measures, together with results from the serum‐induced basophilhistamine release assay (s‐BHRA), were correlated to information ondemographics, clinical characteristics, patient reported outcomes and labora-tory analyses.Results: The histamine content per basophil was significantly differentbetween s‐BHRA positive and ‐negative patients (0.175 vs. 1.40 pg/cell,p < 0.001) and showed a significant negative correlation to the degree ofbasophil activation in s‐BHRA (ρ = −0.209, p = 0.036). Furthermore, theamount of histamine in individual basophils was found to be significantlycorrelated with levels of total cellular blood histamine (ρ = 0.376, p < 0.001),eosinophil counts (ρ = 0.205, p = 0.040), levels of thyroid stimulating hormone(ρ = −0.246, p = 0.014) and titre of antibodies against thyroid peroxidase(ρ = −0.216, p = 0.031) and thyroglobulin (ρ = −0.203, p = 0.044).Conclusions: Low content of intracellular histamine in circulating basophilsis associated with known markers of type IIb autoimmune CSU. Furtherstudies are required to assess whether the amount of histamine in basophilscan be used to monitor or predict response to treatment in patients.