Presence of HLA- B*57:01 is associated with hypersensitivity to Abacavir, a highly effective drug used to treat HIV infection and AIDS. Hypersensitivity reactions usually occur during the first 6 weeks of treatment and include skin rashes, gastrointestinal and respiratory symptoms. Fatalities have also been reported with Abacavir. This allele is also associated with 80 fold increased risk of liver injury when treated with Flucloxacillin. Although the negative predictive value of the test is high, a negative result does not preclude the development of an allergic response to Abacavir and cannot substitute for clinical vigilance whenever Abacavir is administered.