Human Leukocyte Antigen Gene Testing and Carbamazepine-Induced Toxic Epidermal Necrolysis: A Study of Pediatric Practice

Background Stevens–Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are life-threatening drug-induced dermatologic conditions. SJS/TEN occurs in 1-10 per 10 000 patients taking carbamazepine (CBZ) (Pratt VM, McLeod HL, Rubinstein WS et al. Medical Genetics Summaries. National Center for Biotechnology Information US; 2018: 1-527). The development of SJS/TEN is associated with variable drug metabolism and presence of an at-risk HLA haplotype. HLA-B*15:02 and HLA-A*31:01 haplotypes can produce a hyperimmune response in the setting of CBZ use in patients of Asian and European descent, respectively (Schneider JA, Cohen PR. Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis: A concise review with a comprehensive summary of therapeutic interventions emphasizing supportive measures. Adv Ther. 2017; 34:1235-1244). Objective The US Food and Drug Administration (FDA) and the Canadian pharmacogenomics Network for Drug Safety (CPNDS) recommend that patients with high-risk ethnic backgrounds should be genetic tested before initiating CBZ (Sukasem C, Chaichan C, Nakkrut T et al. Association between HLA-B Alleles and Carbamazepine-induced maculopapular exanthema and severe cutaneous reactions in Thai patients. Journal of Immunology Research. 2018; 1-11).We sought out to assess the awareness of this in prescribing practitioners and their standard of practice. Methods We created a 15-question survey and distributed to pediatric neurologists and pediatricians at the University of Alberta. We hypothesized that there was a discordance between the standard of practice and the recommendation by the FDA and CPNDS. Results The survey results indicated a lack of awareness of the at-risk ethnicities for CBZ-induced SJS/TEN. HLA gene testing was rarely done prior to initiation of CBZ in high-risk patients. In addition, there was a lack of awareness for standard of care for genetic testing in Canada and worldwide. Conclusions Our results demonstrate an evident gap between current prescriber practices and existing FDA and CPNDS recommendations to screen for HLA genotypes. We hope that this study captures the realistic potential to improve patient outcomes.