Thiopurine Metabolite testing for Doctors and Pathology Companies

Lab photoGeneral Information

The Eastern Health Inflammatory Bowel Disease (IBD) Clinic works in conjunction with Eastern Health Clinical School, Monash University, to provide leading care for patients with Crohn’s disease and Ulcerative Colitis. As part of our aim to continuously improve our services we provide novel investigations which enhance the management of IBD. This includes measurement of thiopurine metabolites for optimising the dose of azathioprine and 6-mercaptopurine.

Thiopurines, either Azathioprine (also known as Imuran) or 6-mercaptopurine (6-MP or Puri-Nethol) are medications routinely used to manage Crohn’s disease and ulcerative colitis, and may also be used in other autoimmune diseases including Auto-immune Hepatitis, rheumatoid arthritis and after organ transplants. Although most people respond well to these drugs, we know that a proportion do not metabolise it properly and therefore can be at risk of side effects or, do not see benefits to their illness accordingly. Measurement of thiopurine metabolites can aid in optimising the dose and finding out the reason for treatment failures and avoid side effects. However, it does not replace the need to regularly monitor white blood cell counts for leucopenia and LFTs for the duration of therapy with thiopurines.

Thiopurine metabolite testing is routinely used for:

  • Dose Optimisation of thiopurine
    • If remission is not achieved on the current dose, finding safe, higher dose if possible;
    • When side effects occur, determining dose reductions without losing effectiveness;
    • Establishing if non-response or side effects are due to “shunting”;
    • If “shunting”, finding the right thiopurine/allopurinol dose combination;
    • For high risk patients, monitoring dose increases during treatment;
  • Monitoring (non-) adherence to thiopurine
  • Establishing non-response
    • Ensuring treatment isn’t changed too early

Protocol for Blood Collection and getting tests to us for analysis:

Referral forms from any pathology company can be used provided they adhere to the following:

  • 2 x 4mL of blood in EDTA tubes is required at minimum;
  • Do not SPIN or FREEZE the blood
  • Keep sample at 4 degrees Celsius
  • Transport to Eastern Health within the 4 day stability timeframe to make sure analysis is accurate. Any samples received OUTSIDE this time frame will be discarded and the Pathology Company notified for recollection.
  • No fasting is required
  • There is NO time of day requirement for taking of blood samples and, there is no need to consider the time medication was last taken.
  • To stop confusion it is preferred if the referral slip from the doctor & pathology company do not state the word TPMT or Thiopurine Methyltransferase as we do not conduct this enzyme activity testing. It is acceptable to state any of the following on the referral when requesting our testing; Thiopurine
    testing/metabolites/levels, Azathiopurine test¬ing/metabolites/levels, Aza testing/metabolites/levels, Imuran testing/metabolites/levels, 6-thio¬guanine (6TG/6TGN), 6-methylmercaptopurine (6MP/6MMP).
  • Transport sample to (doctors may like to put for pathology to send to Eastern Health on the referral):

Eastern Health Pathology
Level 5, Box Hill Hospital
Nelson Rd Box Hill VIC 3128


The cost for the metabolite testing is $145.00 and will be billed to the Pathology Company. Eastern Health Patients are billed at a discounted rate.

This test is now considered the standard of care in the use of thiopurines in IBD. As is the case with “cutting-edge” tests and technology, currently there is no Medicare reimbursement for these tests. Our prices are kept as low as possible and cover the associated laboratory costs only,to ensure the tests are available to as many patients as possible.


Reports are sent via the requesting Pathology Company. Due to the complex nature of the test, the turn-around time for the results is up to 2 weeks.

Click here for an example of our thiopurine report.

Laboratory Contact details

Monash University, Eastern Health Department of Gastroenterology
IBD Gastroenterology Laboratory
Level 1, 5 Arnold St, Box Hill 3128
Ph: 03 9895 4632

Additional Information