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Test Code BLOD0645 Methotrexate

Important Note

Testing performed by appointment only.  Please call Bozeman Health Laboratory Services Chemistry Department at 414-5010 to schedule Methotrexate testing.

Useful For

  • Determining whether the therapeutically administered Methotrexate drug is being cleared appropriately
  • Verify that a nontoxic Methotrexate concentration has been attained
  • Methotrexate is used in the treatment of certain neoplastic diseases, severe psoriasis, and adult rheumatoid arthritis.

Methodology

Enzyme Immunoassay

Performing Laboratory

Bozeman Health Laboratory Services

Specimen Requirements

Specimen Type: Plasma
Container/Tube: Light-green top (lithium heparin gel)
Specimen Volume: 2 mL
Specimen Minimum Volume: 1 mL

Collection Instructions: Spin down and separate cells within 2 hours of collection.  Ensure adequate centrifugation,  Fibrin, red blood cells and particulate matter may cause erroneous results.  Avoid repeated freeze/thaw cycles.

Specimen Rejection: Specimens from patients who have received glucarpidase (carboxypeptidase G2) as a high-dose methotrexate rescue therapy should not be tested with this immunoassay.

Additional Information

Specimens from patients who have received glucarpidase (Voraxaze, carboxypeptidase G2) as a high dose methotrexate rescue therapy should not be tested with this method. These patients have an increased level of metabolite that cross reacts with the methotrexate antibody. These metabolites stay in circulation for 5-7 days.

Specimen Transport Temperature

Ambient/Refrigerated

Specimen Stability

 

Specimen Type Temperature Time
Plasma Ambient 24 hours
  Refrigerated 14 days
  Frozen 1 month

 

Reference Values

Nontoxic drug concentration after 72 hours: ≤0.10 umol/L

Day(s) Test Set Up

Monday through Sunday, by appointment only

Test Classification and CPT Coding

80299