HLA-B*5701

Genetic testing for abacavir hypersensitivity is recommended before starting anyone on on the NRTI drug abacavir. The presence of the B*5701 allele increases susceptibility to abacavir hypersensitivity. 

The major histocompatibility complex (MHC) family of genes codes for a highly variable set of cell surface glycoproteins (also called human leukocyte antigens or HLAs) that play a critical role in presenting antigens to T-cell receptors to elicit an immune response. Usually a blood sample of 7ml whole blood or four buccal swabs is required for this test.

Even after someone tests negative for this allele, careful monitoring of any person on abacavir is necessary. Occasionally, even a person who has tested B*5701 negative can have a serious hypersensitivity reaction to abacavir.

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