Hypersensitivity reaction (HSR), associated with the antiretroviral abacavir, does not usually have serious outcomes unless recognised late or after rechallenge. Pharmacogenetic testing of human leucocyte antigen (HLA) B*5701 for HSR risk is being used increasingly in clinical practice backed by strong evidence among Caucasians and Hispanics.¹ In the Western Australian landmark studies, updated to improve diagnostic accuracy, positive predictive values (PPVs) and negative predictive values (NPV) of B*5701 for HSR were 78.9% and 99.4%,¹ respectively. When B*5701 screening was introduced into this cohort,² and in Brighton, UK,³ no HSRs were observed in 148 and 185 B*5701 negative patients, respectively, treated with abacavir.

However, associations between B*5701 and HSR have not been adequately investigated in black Africans who represent a substantial proportion of patients infected with HIV in the UK, perhaps resulting in the test being used in these populations without appreciation of screening effectiveness. The potential problem is illustrated by estimations of “numbers needed to screen” summarised in table 1.

In Brighton, among the relatively small numbers from black (predominantly African) ethnicity, the B*5701 carriage rate was recently reported to be 5.3% (high for black Africans).³ …