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Alias Names: Thiopurine methyltransferase enzyme
Methodology: High Performance Liquid Chromatography (HPLC) / TPMT enzyme activity in peripheral RBC
Edit Date: 7/23/2010
Performed: Varies
Released: 3 days after setup at PeaceHealth Laboratories’ reference lab
CPT Code: 82491-90 / 82657-90
Specimen Collection Details
Collection: Two 4 mL lavender top tubes (EDTA).
Handling: Keep as whole blood; do not spin. Keep cold on ice.
Stability: 24 hours ambient, or 8 days refrigerated. Unstable frozen.
Standard Volume: 5 mL whole blood
Minimum Volume: 3 mL whole blood
Transport: Refrigerated.
Comments: TPMT Enzyme provides information to determine candidacy for thiopurine therapy, and to identify patients who may require an alternative dosing strategy. Enzyme level determinations are valuable in stratifying potential therapeutic response, identifies patients in whom thiopurine therapy should be avoided and helps reduce the risk of leukopeina.
Rejection Criteria: Specimen other than specified above; frozen specimen.

Reference Range:
Normal TPMT Acitivity >21.0 EU/mL
Intermediate TPMT Activity 6.0-21.0 EU/mL
Low TPMT Activity <6.0 EU/mL

PeaceHealth Laboratories