Alpha-gal sensitization rates similar among patients with, without chronic urticaria

Alpha-gal sensitization did not appear prevalent among patients with chronic urticaria, with few patients experiencing clinically relevant alpha-gal allergy, according to a letter published in Clinical and Translational Allergy.

Led by Helena Swee-Lin Trige Pedersen of the department of dermato-venereology and the Wound Healing Centre at Copenhagen University Hospital, the researchers examined patients with chronic urticaria — including 373 patients from a primary care allergology practice and 283 from a tertiary hospital dermatology department — as well as 77 patients with allergic diseases other than chronic urticaria as a control group.

Based on serum specific-IgE levels of 0.35 kU/L and higher, 5.6% (n = 21) of the patients from the private practice, 3.9% (n = 11) of those from the hospital and 5.2% (n = 4) of the control group were sensitized to alpha-gal.

Specifically, 4.8% of the patients from the private practice were classified as having class 2 sensitization with sIgE levels of 0.7 kU/L or higher, 2.4% were class 3 with sIgE of 3.5 kU/L or higher and 1.9% were class 4 with sIgE of 17.5 kU/L or higher. Classifications among the patients from the hospital group included 2.8% at class 2, 1.4% at class 3 and 0.4% at class 4.

Researchers detected relevant alpha-gal allergy — based on whether the patient had experienced systemic anaphylaxis, urticaria and/or angioedema within 12 hours of eating red meat — in eight patients from the private practice and two patients from the hospital.

Characteristics that appeared more common among alpha-gal-sensitized patients included male sex (47.6% vs. 24.7%; P = .02), obesity (33.3% vs. 23.6%) and frequent angioedema (61.9% vs. 51.4%) in the private practice group, and male sex (72.7% vs. 27.9%; P = .003) and higher total IgE (median, 168 kU/L vs. 70.5 kU/L; P = .022) in the hospital group.

Six patients had a history of tick bite, but none of them had ever been diagnosed or suspected to have been infected with Borrelia, nor did any of them have elevated IgE against Borrelia.

Overall, these data show that 46 patients in private practice and 141 of patients in a tertiary hospital setting would need to undergo screening to detect one case of clinically relevant alpha-gal allergy.

Based on these totals, the researchers concluded that routine screening for alpha-gal sensitization among patients with chronic urticaria is relatively resource demanding, with only a small subgroup of patients with specific characteristics constituting a relevant population for aimed testing.