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Test Code
TMRBC
Test Name
Thiopurine Methyltransferase, RBC
CPT Codes
84433
Expected Turnaround Time
7 - 12 days
Clinical Utility

Determination of TPMT levels that may be associated with toxicity of anticancer and anti-inflammatory drugs.
Specimen and Container Info

Specimen Type: Whole Blood

  

Collection Container: Lavender Top (EDTA)

Alternate Collection Container: Green Top (Sodium Heparin)

Desired Specimen Volume: Adults 8 mL; Pediatric 5mL
Collection Instructions

Adults:

  1. Collect 3 lavender top (EDTA) tubes via venipuncture.

Pediatric:

  1. Collect 2 lavender top (EDTA) tubes via venipuncture.
Processing and Submission Instructions

Adults:

  1. Transport 8 mL of whole blood in the original collection containers.

Pediatric:

  1. Transport 5 mL of whole blood in the original collection containers
Transport Instructions

Transport to the laboratory refrigerated. 
Stability Requirements

Refrigerated

14 days
Causes for Rejection
  • Frozen specimen
  • Gross hemolysis
  • Clotted specimen
Methodology
Enzymatic endpoint/liquid chromatography/tandem mass spectrometry (LC/MS-MS)
Reference Intervals

See patient report.
Limitations

For patients having an intrinsic low level of TPMT, recent RBC transfusion can variably increase their assayed enzymatic activity depending on the amount and circulating half-life of the transfused red blood cells.
Alternate Names
  • TPMT Biochemical Assay, Myelotoxicity
  • Thiopurine Methyltransferase (TPMT), Enzyme Activity, Erythrocytes
Reference Lab
Labcorp Of America Holdings
Testing Schedule
Routine, 3 times per week
The American Medical Association (AMA) Current Procedural Terminology (CPT) codes published by HNL Lab Medicine are guidelines and are intended for informational purposes only. CPT coding is the exclusive responsibility of the billing entity. View the Terms.
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