Long-term reproducibility of positive patch test reactions in patients with non-immediate cutaneous adverse drug reactions to antibiotics

Background: As in contact allergy, T cell-mediated hypersensitivity in non-immediate (NI) cutaneous adverse drug reactions (CADRs) to antibiotics is considered to be lifelong, but, in this setting, patch tests have rarely been repeated after long time intervals.

Objective: To evaluate the long-term reproducibility of positive patch test reactions to antibiotics in patients with NI CADRs.

Methods: Fifty-six patients with NI CADRs to antibiotics who had relevant positive reactions during patch testing were invited to repeat patch tests with a similar antibiotic series 2-15 years thereafter.

Results: Twenty patients were included (9 males and 11 females; mean age 54.6 years): 18 with maculopapular exanthema, 1 with drug hypersensitivity syndrome, and 1 with acute generalized exanthematous pustulosis. Results were reproducible in 17 of 20 patients after a mean interval of 6.0 years (range 2-14.7 years). Concerning β-lactams, 7 of 8 patients remained positive for aminopenicillins, 4 of 4 for isoxazolyl penicillins, and 1 for cefoxitin. Patch test results were also reproducible for clindamycin in 5 of 7 patients, for vancomycin in 1 patient, and for spiramycin in 1 patient. Reproducibility was not affected by the time interval between tests, sex, or age at testing.

Conclusions: In the context of NI CADRs, we showed high reproducibility of positive patch test reactions to various antibiotics, even after several years.