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Also known as: B5701

Test category:

Immunology - Hypersensitivity; Pharmacogenomic - Hypersensitivity

Use of test


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.

Abacavir must never be prescribed to a patient with HLA*B57:01. Patients must be screened for this variant before being commenced on abacavir.


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 must never be prescribed to a patient with HLA*B57:01. Patients must be screened for this before being commenced on abacavir.

Ethical considerations:

This test has a role in identifying patients who may benefit from avoiding a specific drug or dose, but it provides little useful information for people (including relatives) who are not taking the medications of concern. Testing of relatives is generally not recommended.


Analysis of the gene sequence of the HLA-B genes for the presence of this specific variant.

Requesting the test


This test can be requested by any medical practitioner.

Sample required:

4 mL blood in EDTA. Specimens may be collected by the requesting practitioner or at any Sonic Healthcare collection centre (see link below).

To help ensure the quality of the test, a genetic test should be done with a dedicated sample whenever possible i.e. a sample collected specifically for that test rather than a sample that is used for multiple tests.

We recommend that the patient or another adult check the labelling of request forms and sample tubes. 

>Link to Sonic Healthcare collection centres

Turnaround time:

2 business days.


This test has a Medicare rebate which, subject to the requirements of the Medicare descriptor being met, may cover all or part of the cost.


The Medicare details, including descriptor and schedule fee, are listed under MBS item 73323.

Click here for our billing policy.