In July 2008, the U.S. Food and Drug Administration (FDA) issued a post-marketing communication [15] to update the prescribing information for abacavir.  The updated black box warning stated “Prior to initiating therapy with abacavir, screening for the HLA-B*5701 allele is recommended; this approach has been found to decrease the risk of hypersensitivity reaction” [16]. This evidence concerns the gene HLA-B and hypersensitivity reaction disease.