Methotrexate Assay
Order Code: MTXL
Epic Lab Code: LAB481
Order Form: A-1a Therapeutic Drug Analysis or Epic Req
Chemistry
6240 RCP
356-3527
Specimen:
Plasma
Collection Medium:
Plasma Separator Tube
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.
Delivery Instructions:
Deliver to laboratory immediately after collection. Protect specimen from light.
Testing Schedule:
24 hrs/day, 7 days a week, including holidays.
Analytic 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.
Comments:
Methotrexate units changed 12/7/2009 from mol/L (molar) to umol/L (micromolar). 1 umol/L = 1 x 10exp-6 mol/L. Analytical method changed 12/9/2010.
Test Limitations:
The test is cancelled when the following indices are exceeded: hemolysis - 800, lipemia - 1000, and icterus - 30. Methotrexate concentrations less than 0.1 umol/L are reported as "< 0.1 umol/L".
Methodology:
EMIT (Enzyme-multiplied immunoassay technique)
CPT Code:
83520
 
See Additional Information:
Specimens Requiring Immediate Delivery