Risk Factors

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

The risk for abacavir HSR is higher 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.

Patient's HLA-B*5701 status must always be documented 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.

The HLA-B*5701 allele is more common among patients who have a suspected hypersensitivity reaction to abacavir compared with those who do not.

No other pharmacogenetic markers have been found that identify patients at risk of abacavir hypersensitivity in all ethnic groups and in both sexes.

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