TPMT activity is predictive of the risk of severe myelosuppression during treatment with azathiopurine, 6-mercaptopurine and related thiopurine compounds.
TPMT Genotyping is preferred to phenotyping as a first line test. If special circumstances warrant phenotype testing, this must be discussed directly with the external testing laboratory (ICPMR Molecular Diagnostics Laboratory, ph: 02 8890 7651).
Request slips for phenotyping should indicate that approval has been given to avoid unnecessary transportation costs for a request that will not be performed.
