Risk Factors

Carriage of HLA-B*5701 is a known risk factor

Risk of abacavir HSR is high for patients who test positive for the HLA-B*5701 allele. However, abacavir HSRs have been reported at a lower frequency in patients who do not carry this allele.

HLA-B*5701 status must always be documented and explained to the patient prior to initiating therapy.

Abacavir should never be initiated in patients with a positive HLA-B*5701 status, nor in patients with a negative HLA-B*5701 status who had a suspected abacavir HSR on a previous abacavir-containing regimen.

No other pharmacogenetic markers have been found that identify patients at risk of abacavir hypersensitivity.

 HLA-B*5701 is not always present in people who have a suspected abacavir HSR.