Methotrexate


Abbrev Code:MTX   
Order Code:LAB481Order Name:Methotrexate Level
Synonyms:Mexate
Methodology:ARK homogeneous enzyme immunoassay
Vista: Enzyme immunoassay
CPT Codes: 80204 x1, 80204 x1
Turnaround Time:Performed and reported 24 hours/day
Associated Links:

Roche Go Live schedule



Collection Instructions

Specimen:Blood
Optimal Volume:1 mL
Minimum\Peds Volume:0.4 mL
Container:Purple (EDTA) protect from light
Alternate Containers: Red (no gel) protect from light
Collection Instructions:Test is light sensitive, therefore wrap collection tube in foil or paper towel immediately after collection.
Causes for Rejection:Not protected from light.


Processing and Shipping

Specimen Processing:Centrifuge and aliquot 0.5 mL, 0.1 mL minimum into a light protected vial. Store in refrigerator.
UMMC East: Decant and add pre-printed "STAT MTX" label to the aliquot tube.
Shipping Instructions:Ship at refrigerated temperature; protect from light and temperature extremes.
Stability:Roche: 2 weeks refrigerated; samples may be stored frozen if limited to no more than 3 freeze-thaw cycles.
Vista: 2 weeks refrigerated.
Test Performed at or Referral Lab Chemistry  (Roche-UMMC East, UMMC/UMMCH-West Bank)


Interpretive

Reference Range:Following a 4-6 hour infusion:
24 hour concentration  < 5.0 umol/L
48 hour concentration  < 0.5 umol/L
72 hour concentration  < 0.2 umol/L
Higher levels at the given time ranges may indicate risk of toxicity if conventional low-dose leucovorin rescue is given.
Use:Monitor therapeutic dosing and evaluate toxicity. Plasma levels peak at 1-2 h after oral dose and 30-60 m after I.V. dose. Half-life is approximately 3-4 h.


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