Diagnostic evaluation of patients with nonimmediate cutaneous hypersensitivity reactions to iodinated contrast media.

Background: Nonimmediate hypersensitivity reactions to iodinated contrast media (CM) are common. Allergological evaluation is necessary to confirm the diagnosis and to find a tolerated alternative. The aim of this study was to establish the role of skin testing and the drug provocation test (DPT) in the diagnosis of nonimmediate reactions to CM.

Methods: Skin intradermal testing and patch testing with delayed readings were carried out with different CM (iobitridol, iomeprol, iodixanol, iohexol, ioversol, iopramide and ioxaglate). Single-blind placebo-controlled DPT was carried out in those cases with a negative skin test. In seven cases, a skin biopsy was obtained from positive skin tests and positive DPT.

Results: Of the 161 subjects evaluated, 34 (21.1%) were skin-test positive, 21 (50%) to Iomeprol, 7 (16.7%) to Iodixanol, 5 (11.9%) to Iobitridol, 4 (9.5%) to Ioxaglate, 3 (7.1%) to Iohexol and 1 (2.4%) to Iopramide. DPT was positive in 44 cases (34.6%) that were skin-test negative, 38 (76%) to Iodixanol, 8 (16%) to Iomeprol and 4 (8%) to Iohexol. Of 78 cases (48.4%) with confirmed hypersensitivity, 34 (43.6%) were identified by skin testing and 44 (56.4%) by DPT. Skin biopsies showed a perivascular mononuclear cell infiltrate, mainly in the dermis, with higher levels of CD4 than CD8 T lymphocytes, with expression of activation markers and skin homing receptors.

Conclusion: Patients with nonimmediate reactions to CM were identified by skin testing in 43.6% and by DPT in 56.4%. The method to confirm the diagnosis differed depending on the CM involved.