Methotrexate Post Glucarpidase, Serum
Use
This test is useful for monitoring methotrexate concentrations in patients who have undergone glucarpidase therapy, which is administered to reduce toxic methotrexate levels. It is crucial for assessing patients who might not respond to treatment due to noncompliance and for guiding dosage adjustments in those with renal failure. Methotrexate is used in various cancer treatments and at lower doses for conditions like rheumatoid arthritis and psoriasis. Monitoring helps ensure therapeutically effective concentrations while minimizing toxicity.
Special Instructions
Specimen should be protected from light; ship in an amber vial. If not ordering electronically, submit a completed Therapeutics Test Request form with the specimen.
Limitations
The test requires that specimens be light-protected to prevent false readings. Handling errors such as exposure to light may lead to specimen rejection. This test has not been cleared or approved by the FDA, as it was developed and its performance characteristics determined by Mayo Clinic in accordance with CLIA requirements. Concentrations that lead to toxic effects can be difficult to predict precisely, and results must be interpreted in conjunction with clinical context.
New York Approved
Methodology
Mass Spectrometry (LC-MS/MS)
Biomarkers
LOINC Codes
- 51602-1
- 51602-1
Result Turnaround Time
1 day
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
1 mL
Minimum Volume
0.5 mL
Container
Amber vial
Collection Instructions
Within 2 hours of collection, centrifuge and aliquot serum into an amber vial. Protect from light.
Causes for Rejection
Exposed to light >24 hours
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 7 days (LIGHT PROTECTED) |
| Refrigerated | 7 days (LIGHT PROTECTED) |
| Frozen | 14 days (LIGHT PROTECTED) |