Methotrexate Drug Level

Label Mnemonic:	MTXL
Epic code:	LAB481
Order form:	Laboratory Requisition
Supply order:	Supply Order Form
Billing:	Billing Policies
CPT code:	83520

Specimen(s):

Plasma

Collection Medium:

Plasma Separator Tube 4.5 mL

Alternate Collection Media:

Call laboratory for additional acceptable specimen collection containers.

Minimum:

3 mL whole blood in light green lithium heparin tube or ONE Microtainer^®.

Testing Schedule:

24 hrs/day, 7 days a week, including holidays.

Turn Around Time:

1 hour (upon receipt in laboratory)

Reference Range:

Clinical toxicity following high-dose methotrexate more frequent 
with serum concentrations:
   >  10 umol/L at 24 hrs.
   >   1 umol/L at 48 hrs.
   > 0.1 umol/L at 72 hrs.

Test Limitations:

The test is cancelled when the following indices are exceeded: hemolysis - 1000, lipemia - 500, and icterus - 70. Methotrexate concentrations less than 0.1 umol/L are reported as "< 0.1 umol/L".

Methodology:

EMIT (Enzyme-multiplied immunoassay technique)

Sample Processing:

Centrifuge at a speed and time necessary to get barrier separation of plasma/serum and cells within 1 hour of collection. Send specimen in original tube. Do Not transfer to another tube.
Each sample must be labeled with at least TWO full patient identifiers (First/Last Name & DOB are sufficient for non-UIHC affiliated clients) to avoid sample rejection/delays.

Sample Storage:

Refrigerate.
All sample storage requirements are intended for delivery to UIHC within 24 hours of collection for testing. If samples won't arrive in this time period, please call the UIHC Core Lab for alternative storage/shipping instructions (319-356-3527).

Transport Instructions:

Place labeled specimen into zip-lock type biohazard bag; seal bag.
Place completed requisition into outside pocket of bag.
Transport in cooler with refrigerated coolant packs.