Our Tests

TPMT Screen

Also known as: TPMT

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The protein thiopurine methyltransferase breaks down the thiopurine-based immunosuppressive drugs. Variants in the protein’s gene, TPMT, can reduce the activity of the protein, resulting in toxic levels of the drug and bone marrow suppression. The drugs involved are

  • azathioprine
  • 6-mercapto-purine (6MP)

This test identifies almost all patients at risk of neutropenia from these medications

Other side effects such as GIT upset (with or without pancreatitis) are not identified by this test.

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.

Clinical Utility

The laboratory report will define the gene variants present in a patient, and identify persons at increased risk of profound neutropenia.



Test Method

Analysis of the TPMT gene.

Test Ordering

This test can be requested by any medical practitioner.

5 mL blood in EDTA. Specimens may be collected by the requesting practitioner or at any Sonic Healthcare pathology collection centre.

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

Special Instructions

Please list current and proposed medications on the request form. Please highlight any medications that have caused problems in the past.



This test may have a rebate for all or part of the cost.

Medicare Rebate

This test has a Medicare rebate of $44.20, subject to the requirements of the Medicare descriptor being met. The MBS item number is 73327.

Turnaround Time

5 working days.