Skin Test Results and Cross-Reactivity Patterns in IgE- and T-Cell-Mediated Allergy to Gadolinium-Based Contrast Agents.

Allergies to gadolinium-based contrast agents (GBCAs) are rare and manifest usually as an immediate drug hypersensitivity reaction (DHR), compatible with an immunoglobulin E (IgE)-mediated mechanism. Although the molecular structures of GBCA show some similarities and are either linear or macrocyclic, the frequency and pattern of cross-reactivity remain unclear. However, cross-reactivity has been described. The aim of this investigation was to assess cross-reactivity in patients with GBCA allergy based on skin tests and exposure. We retrospectively evaluated a total of 28 cases with a proven allergy to a GBCA, including 11 from the database of the allergy division of the Inselspital, Bern and 17 published cases from the literature, retrieved with a PubMed-MEDLINE search. The majority of cases were immediate DHR, with 8/11 cases from the database (72.7%) and 16/17 published cases (94.1%). In both groups macrocyclic GBCA were most often identified as causative drugs. A cross-reactivity based on skin test results was found in 2 out of 11 database cases (18.2%) and in 6 out of 17 literature cases (35.3%). Cross-reactivity occurred within macrocyclic GBCA in 1/11 database cases and 3/17 literature cases, and included both macrocyclic and linear GBCA in 1/11 and 4/17 subjects. There was no cross sensitization among linear GBCA. Skin test-negative GBCA were well tolerated, even in cases with sensitization to linear and macrocyclic GBCA. Overall, cross-reactivity in GBCA allergy is rare (approximately 29%), and may occur among macrocyclic GBCA or in between macrocyclic and linear GBCA. IgE to linear GBCA seems to be rarely cross-reactive. Skin test is helpful in identifying safe alternatives, as no reaction to skin test-negative GBCA was observed.