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Example clinical scenario

A 25-year-old man of Han Chinese origin requires carbamazepine for the treatment of epilepsy. The risk of carbamazepine-induced severe cutaneous reaction may be increased due to his ethnic origin.

When to consider genomic testing

  • HLA-B*15:02 and HLA-A*31:01 have distinct ethnic and geographical distributions that are important for evaluating population risk. While severe cutaneous reactions are estimated to occur in between 1 and 6 per 10,000 new users of carbamazepine in countries with mainly White populations, the risk in some Asian populations is thought to be up to 10 times higher. Associations between HLA-B*15:02 and HLA-A*31:01 and carbamazepine hypersensitivity have been recorded in children as well as in adults.
  • The summary of product characteristics for carbamazepine (sold under the brand name Tegretol) indicates that patients of Han Chinese and Thai origin should, whenever possible, be screened for HLA-B*15:02 before starting treatment, but that there is insufficient data to support a recommendation for HLA-A*31:01 screening. Prior screening for HLA-B*15:02 in patients of Han Chinese, Hong Kong Chinese and Thai origin was also recommended by the Medicine and Healthcare products Regulatory Agency in 2008.

What do you need to do?

  • At the time of writing, the National Genomic Test Directory does not include pharmacogenomic testing for HLA-B*15:02 or HLA-A*31:01 variants, although tests may be available via your regional Genomic Laboratory Hub or other local laboratories (such as histocompatibility or immunogenetics laboratories).
  • For human leukocyte antigen (HLA) testing (and other DNA-based tests), an EDTA sample is required.
  • For more information on genomic testing for the HLA-B*15:02 and HLA-A*31:01 variants, including how identification of these alleles affects patient management, see Results: Patient requiring carbamazepine with a known variant in the HLA-B*15:02 or HLA-A*31:01 allele.
  • Information about patient eligibility and test indications was correct at the time of writing. When requesting a test, please refer to the National Genomic Test Directory to confirm the right test for your patient.

Resources

For clinicians

References:

For patients

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  • Last reviewed: 02/07/2024
  • Next review due: 02/07/2025
  • Authors: Nicola Husain and Fan Cheng
  • Reviewers: Dr Charlotte Barker, Professor Bill Newman