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Laboratory: Clinical Biochemistry
Test Name:
Test Code: MIS8
Clinical Information:
Test Indications: This test may be used as an alternate testing for acute thiopurine toxicity in patients who received multiple red blood cell transfusions prior to testing.
NOTE: only screens for common mutations.
Recommended screening test for azathioprine and 6-mercaptopurine induced leucopenia is Thiopurine Methyltransferase (TPMT), Enzyme Activity (Phenotype), Erythrocytes – (B) (test code: TPMP)

Test Approval Requirements: F260-11-02 Biochemistry Approval for Test Referral Form
Exception: Test approval is not required for requests from Oncology specialists.
Collection Devices:
Transport specimen to lab on ice (to prevent specimen from freezing, wrap specimen in paper towel and place on ice). Patients should be tested prior to azathioprine or 6-MP administration.
Specimen Required:
Whole Blood: 3.0 mL
Pediatric Whole Blood: 3.0 mL

Collection Information: 
1. Invert several times to mix blood.
2. Send whole blood specimen in original tube. Do not aliquot.
Collection Information: Do not centrifuge. Do not freeze.
Specimen Stability: 
Ambient: 24 hours
Refrigerated: 7 days
Frozen: unacceptable
Whole Blood: 3.0 mL

Shipping & Storage: Send in original collection tube. Store and ship whole blood at room temperature (preferred) or refrigerated. Do not freeze.
Specimen must be received at the testing site within 7 days of collection.
Referred Out Location: Specimen referred from HSC-MS5 to:
In-Common Laboratories (ICL)
57 Gervais Drive
North York, Ontario
M3C 1Z2
Telephone: (416) 422-3000
Test Name: Thiopurine Methyltransferase (TPMT) Genotype, Blood
Testing location: Sunnybrook Hospital, Toronto, ON, Canada
Reference Values:
An interpretive report will be provided.
Method of Analysis: PCR
Within 3 Weeks
See Also:
More Information: