TPMT Stripassay

The Viennalab TPMT StripAssay determines the genotype of thiopurine S-methyltransferase (TPMT) in order to guide the dosing of thiopurine drugs.

Clinical background

Azathioprine, 6-mercaptopurine and 6-thioguanine are used in the treatment of leukaemia and of autoimmune disorders, and in immunosuppression after organ transplantation. TPMT inactivates these drugs. Carriers of a reduced-function allele accumulate active metabolites, which leads to myelosuppression at a standard dose. The genotype indicates whether the dose has to be lowered or another drug chosen.

Alleles covered

The strip distinguishes the wild-type allele *1 and the variant alleles *2, *3A, *3B and *3C. These are read from the three variant loci 238G>C, 460G>A and 719A>G. Clinical dosing guidance for the corresponding drugs is published by CPIC and listed in PharmGKB.

Method

The assay uses PCR amplification with biotinylated primers followed by reverse hybridisation to probes immobilised on a test strip, with a colour reaction for detection. The kit contains the lysis solution and GENxTRACT resin for releasing DNA from whole blood; further DNA extraction reagents are not supplied with the kit, and ViennaLab recommends the Spin Micro DNA Extraction Kit (REF 2-020) or the GENxTRACT Blood DNA Extraction System (REF 2-014), ordered separately.

• Lysis Solution (50 ml)
• GENXTRACT Resin (5 ml)
• Amplification Mix (yellow cap, 500 µl)
• Taq Dilution Buffer (transparent cap, 500 µl)
• DNAT (blue cap, 1.5 ml)
• Typing Trays (3)
• Teststrips (20)
• Hybridization Buffer (white cap, 25 ml)
• Wash Solution A (white cap, 80 ml)
• Conjugate Solution (25 ml)
• Wash Solution B (80 ml)
• Color Developer (25 ml)
• Instructions For Use (1)
• Collector Sheet (1)

Kit for 20 tests, REF 4-740. DNA extraction reagents are not supplied with the kit. ViennaLab recommends the Spin Micro DNA Extraction Kit (REF 2-020) or the GENxTRACT Blood DNA Extraction System (REF 2-014), which are ordered separately.