What is being tested?

The human leukocyte antigen (HLA) genes are part of the immune system and are involved in the recognition of foreign substances such as drugs, viruses and bacteria. The HLA-B gene is one type of HLA molecule and more than 1,500 different HLA-B alleles have been identified. One particular allele; HLA-B*57:01 is associated with an increased risk of being allergic to the anti-HIV drug abacavir.  

How is it used?

A specific variant of the human leukocyte antigen B57, HLA-B*57:01, is associated with severe cutaneous adverse reactions (SCAR) to the medication, abacavir. Patients who have this gene variant and take abacavir are very likely to develop a fever, severe rash, abnormal blood count, hepatitis, and kidney inflammation. If a person has this variant, the risk of developing a severe cutaneous adverse reaction (SCAR) to abacavir is approximately 99.9%. If a person does not have this specific variant, the risk of SCAR is negligible. Abacavir is not used in people who carry the HLA*B57:01 variant.

When is it requested?

Patients must be screened for this variant before being commenced on abacavir.

What does the result mean?

Abacavir must never be prescribed to a patient with HLA*B57:01.

The presence of this variant is not associated with any other disease.

Is there anything else I should know?

Abacavir is commonly used as an effective treatment for HIV infection. For patients with the HLA-B*5701 variant, there are other medications which can be used instead of abacavir.

Common questions

• Can HLA-B*5701 cause problems other than sensitivity to abacavir?

This variant is not known to be associated with any other disease or risk of disease.

• How common is the HLA-B*5701 variant?

The frequency of this variant varies from 7-20% in different ethnic groups.

• What can I do to take care of myself if I have HLA-B*5701 variant?

There is no need to take any precautions other than avoid taking abacavir.

More information

Genetic Home Reference: HLA-B