Prevalence of abacavir-associated hypersensitivity syndrome and HLA-B*5701 allele in a Portuguese HIV-positive population

Background: Human Immunodeficiency Virus (HIV)‐positive patients treated with the antiretroviral drug abacavir (ABC) may develop a potentially fatal ABC‐associated hypersensitivity syndrome (ABC‐HS), typically characterized by fever, malaise, rash, vomiting/diarrhoea and/or dyspnoea/cough. ABC‐HS has been strongly associated with HLA‐B*57:01 carriage and screening for this allele is recommended. Objective: To determine the prevalence of HLA‐B*57:01 and to characterize suspected ABC‐HS in the adult HIV population from our hospital during a 7‐year period. Methods: Clinical data on patients under ABC treatment from January 2006 to December 2012 were analyzed to search for symptoms of ABC‐HS. Reactions of suspected ABC‐HS were characterized. HLA‐B*57:01 and patch tests (1% and 10% ABC in petrolatum) with readings at 48 h were performed in those without previous testing. From January 2008 routine HLA‐B*57:01 screening was implemented. Results: From January 2006 to December 2007, 186 patients began treatment with ABC (data from 163 were available): 7 (4%) patients stopped ABC for suspected ABC‐HS (71% males, median age 45 years) and the median time for onset of the reaction after starting ABC was 7 days. Four of the 7 patients had the HLA‐B*57:01 allele and 2 of these 4 had positive patch tests. After HLA‐B*57:01 screening implementation (January 2008), 573 patients were evaluated and 35 (6.1%) were HLA‐B*57:01 positive; no suspected ABC‐HS were observed since then. Conclusion: Four patients with suspected ABC‐HS (of 6 screened) were HLA‐B*57:01 positive. No ABC‐HS occurred since January 2008, after HLA‐B*57:01 screening was implemented.