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Test Code MTXSG Methotrexate Post Glucarpidase, Serum

Reporting Name

Methotrexate Post Glucarpidase, S

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Useful For

Monitoring methotrexate concentrations post-glucarpidase therapy

 

Documenting failure to respond that may be due to noncompliance

 

Guiding dosage adjustments in patients with kidney failure

Method Name

Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)


Shipping Instructions


Ship specimen in amber vial to protect from light.



Specimen Required


Supplies: Amber Frosted Tube, 5 mL (T915)

Collection Container/Tube:

Preferred: Red top

Acceptable: Serum gel

Submission Container/Tube: Amber vial

Specimen Volume: 1 mL

Collection Instructions: Centrifuge and aliquot serum into an amber vial.


Specimen Type

Serum

Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 7 days LIGHT PROTECTED
  Frozen  14 days LIGHT PROTECTED
  Ambient  7 days LIGHT PROTECTED

Reject Due To

Gross hemolysis OK
Gross lipemia OK
Gross icterus OK
Exposed to light >24 hours Reject

Reference Values

Nontoxic drug concentration after 72 hours: <0.1 mcmol/L

Interpretation

Following a 4- to 6-hour intravenous infusion of methotrexate, postinfusion concentrations greater than the following indicate an increased risk of toxicity if conventional low-dose leucovorin rescue is given:

-24-hour postinfusion concentration: 5.0 to 10.0 mcmol/L

-48-hour postinfusion concentration: 0.5 to 1.0 mcmol/L

-72-hour postinfusion concentration: 0.1 mcmol/L

Day(s) Performed

Monday through Sunday

Report Available

Same day/1 day

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information

80204

LOINC Code Information

Test ID Test Order Name Order LOINC Value
MTXSG Methotrexate Post Glucarpidase, S 51602-1

 

Result ID Test Result Name Result LOINC Value
62580 Methotrexate Post Glucarpidase, S 51602-1

Forms

If not ordering electronically, complete, print, and send a Therapeutics Test Request (T831) with the specimen.