Pharmacogenomics

The right drug at the right dose at the right time

This section provides information only about this specific pharmacogenomic test.

Remember:

  • If you have medication questions, ask your health care provider.
  • Follow your health care provider's instructions when taking any medication.
  • Do not change your medications without talking with your health care provider.

HLA-B*5801/Allopurinol Pharmacogenomic Lab Test

Key Facts

  • The HLA-B*5801 gene test is used to identify those at risk for serious side-effects to a medication called allopurinol.
  • A positive test result means you have the HLA-B*5801 gene variant and have a higher risk of developing a potentially life-threatening reaction to allopurinol. Allopurinol is not recommended unless the benefit clearly outweighs the risk.
  • A negative test result means you do not have the HLA-B*5801 gene variant. Allopurinol may be taken.
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Results

What should I do with my test results?

Talk to your health care provider or pharmacist about the results. They may recommend that you:

  • Keep taking a medication
  • Change the dose of a medication
  • Stop taking a medication
  • Take a different medication

What does my HLA-B*5801 result mean?

Positive

This means that you have the HLA-B*5801 gene variant. A different medication should be prescribed. Talk with your health care provider about choosing a medication that is safe for you.

Negative

This means that you do not have the HLA-B*5801 gene variant. Allopurinol may be prescribed. This test does not rule out the possibility of all adverse reactions.

Who will see my results?

Only health care professionals, and those you have given permission, may view your genetic test results. If you are receiving care at another medical facility, Mayo Clinic recommends you share this information with your other health care providers.

How could the HLA-B*5801 test result affect my treatment?

If you test positive for the HLA-B*5801 gene variant, you should not take allopurinol. Your health care provider can help to find an alternative medication that is safe for you.

If you test negative for the HLA-B*5801 gene variant, allopurinol therapy may be recommended. It is still possible for you to have side effects with allopurinol even if you do not have the HLA-B*5801 gene variant. If you have a negative test result and take allopurinol, your health care provider should monitor you routinely for possible side effects.

Who is affected? Do different populations respond differently?

The HLA-B*5801 gene variant is found almost exclusively in individuals with ancestry across broad areas of Asia. Mayo Clinic recommends testing individuals of Asian ancestry before taking allopurinol.

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Medications

What is allopurinol?

Allopurinol is used to prevent or treat high uric acid levels in the blood. Gout or gouty arthritis (inflammation and pain in a joint) is caused by high uric acid levels. Allopurinol is a xanthine oxidase inhibitor that works by causing less uric acid to be produced by the body.

Allopurinol is also used to prevent or treat high uric acid levels that may be caused by cancer medicines or for patients with kidney stones that contain calcium.

Which gene affects my response to allopurinol?

Variants in a gene called HLA-B can affect how you respond to allopurinol. The HLA-B gene has hundreds of variations. Each variation is given a number. People with a certain variant in this gene called HLA-B*5801 have a higher risk of developing serious skin reactions, including the conditions toxic epidermal necrolysis (TEN) and Stevens-Johnson syndrome.

What problems can patients with the HLA-B*5801 gene variant have when taking allopurinol?

Patients with the HLA-B*5801 gene variant can develop toxic epidermal necrolysis or Stevens-Johnson syndrome, which are forms of a rare and serious condition involving the skin and mucous membranes (lining of the mouth and nose).

Toxic epidermal necrolysis is a more serious form of Stevens-Johnson syndrome in which a larger area of the skin or mucous membranes is affected.

Other considerations:

Most patients treated with allopurinol who develop toxic epidermal necrolysis or Stevens-Johnson syndrome have this reaction within the first few months of treatment. If you are of Asian ancestry and have recently started taking allopurinol (less than 3 months ago); your health care provider may consider testing you for the HLA-B*5801 gene variant. If you have been taking allopurinol for more than 3 months without any complications, testing for the HLA-B*5801 gene variant most likely would not be recommended.

Where can I find more information about allopurinol?

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Resources

These resources may help you understand more about individualized medicine, genomics and drug-gene testing (pharmacogenomics):

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Contact

If you have questions about your test results, ask to speak with your health care provider at your Mayo Clinic care location:

  • Minnesota
    507-284-2511
  • Arizona
    480-301-8000
  • Florida
    904-953-2000
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