Test Catalog

Test ID: TPMT3    
Thiopurine Methyltransferase (TPMT) Activity Profile, Erythrocytes

Specimen Type Describes the specimen type validated for testing

Whole blood

Specimen Required Defines the optimal specimen required to perform the test and the preferred volume to complete testing

Patient Preparation: Thiopurine methyltransferase (TPMT) enzyme activity can be inhibited by several drugs and may contribute to falsely low results. Patients should abstain from the following drugs for at least 48 hours prior to TPMT testing: naproxen (Aleve), ibuprofen (Advil, Motrin), ketoprofen (Orudis), furosemide (Lasix), sulfasalazine (Azulfidine), mesalamine (Asacol), olsalazine (Dipentum), mefenamic acid (Ponstel), trimethoprim (Proloprim), methotrexate, thiazide diuretics, and benzoic acid inhibitors.

Container/Tube:

Preferred: EDTA

Acceptable: Green top (sodium heparin), metal free sodium heparin, lithium heparin, or plasma separator tubes

Specimen Volume: 5 mL

Special Instructions Library of PDFs including pertinent information and forms related to the test

Forms

1. New York Clients-Informed consent is required. Document on the request form or electronic order that a copy is on file. The following documents are available in Special Instructions:

-Informed Consent for Genetic Testing (T576)

-Informed Consent for Genetic Testing-Spanish (T826)

2. If not ordering electronically, complete, print, and send a Gastroenterology and Hepatology Client Test Request (T728) with the specimen.

Specimen Minimum Volume Defines the amount of sample necessary to provide a clinically relevant result as determined by the Testing Laboratory

3 mL

Reject Due To Identifies specimen types and conditions that may cause the specimen to be rejected

Hemolysis

Mild OK; Gross reject

Lipemia

NA

Icterus

NA

Other

NA

Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included

Specimen TypeTemperatureTime
Whole bloodRefrigerated (preferred)6 days
 Ambient 6 days