| Collection & Request Instructions: | Used for the identification of patients at risk of myelosuppression prior to initiation of thiopurine drug therapy (e.g. azothioprine, 6-mercaptopurine, thioguanine). We are now sending TPMT tests to PathWest (QEII Medical Centre, WA) who offer a comprehensive, sequential TPMT testing service. TPMT Phenotype, which measures thiopurine methyltransferase activity, is the first-line test and if it is normal no further testing is indicated. If TPMT Phenotype is abnormal, it is automatically followed by the TPMT Genotype test which screens for the common TPMT mutations. There are rare mutations not detected by this Genotype test. An abnormal Phenotype which is not associated with common mutations will prompt sequencing of the entire coding region of the TPMT gene to detect rare mutations. |
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