Drug patch testing in Stevens-Johnson syndrome and toxic epidermal necrolysis

Background : The data on patch testing (PT) to identify culprit medications in Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN) are limited to scattered case reports and small case series, without analysis of overall trends to inform clinicians of its utility, methodology, and safety. Objective : To conduct a systematic review of the practice of PT in SJS/TEN, quantify the positivity rate (PR) of common drug classes, and assess safety during testing. Methods : PubMed was searched from inception to 2021. Search terms included “patch testing” AND “SJS” OR “TEN” OR “Stevens-Johnson Syndrome” OR “Toxic Epidermal Necrolysis” OR “Lyell's Syndrome”. Results : Fifty-eight articles met inclusion criteria. In total, 82 patients underwent patch testing for SJS/TEN, resulting in 104 positive reactions to 49 unique medications. Anti-epileptic drugs were responsible for 48.1% of positive reactions; antibiotics, 28.8%; and NSAIDs, 6.7%. The PRs of anti-epileptics, antibiotics, and NSAIDs were 33.1%, 13.1%, and 21.9%, respectively. When accounting for suspected causality, these rates increased to 54.3%, 77.8%, and 54.5%, respectively. Three patients (3.7%), two of whom were HIV+ with active tuberculosis, experienced systemic reactions during PT, that required only conservative treatment. Conclusion : Published reports suggest that PT in SJS/TEN is useful and safe. AEDs have been tested most frequently and show the highest positivity rate. There is a critical need for large-scale studies with standardized methodology to obtain reproducible data on PT in SJS/TEN.