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

TLDR: 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.

Abstract: SummaryBackground 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.