Methotrexate


Sunquest Code:MTX  
Epic Code:LAB481Epic Name:Methotrexate Level
Order Instructions:See Special Instructions.
Synonyms:Mexate; MTX
Methodology:Enzyme immunoassay
CPT Code:80299
Turnaround Time:Performed and reported 24 hours/day
Special Instructions:
Process MTX specimens at the sending laboratory - centrifuge and aliquot into a light-protected aliquot tube.

Specimens sent to UMMC-East only:
  • Add special pre-printed label to the aliquot tube - "STAT MTX" Must be Decanted."
  • Receiving area "BUDEC" in Sunquest: SMART→Processing→Decant→then "BUDEC" and relabel the sample before delivering to the testing area.

Specimens sent to FSH only:
  • Please notify FSH Laboratory before sending any MTX specimens by calling 952-924-5140 and ask to speak to the Core Technologist.
     


Collection Instructions

Specimen:Blood
Optimal Volume:1 mL
Minimum\Peds Volume:0.4 mL
Container:Purple (EDTA) protect from light (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. Protect from light. Store in refrigerator.
Shipping Instructions:Ship at refrigerated or room temperature; protect from light and temperature extremes.
Test Performed at or Referral Lab Chemistry  (UMMC-East Bank, Fairview Southdale - FSH, UMMC/UMMCH-West Bank)


Interpretive

Limitations: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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