Methotrexate
Test Mnemonic
MTX
CPT Codes
- 80204 - QTY (1)
LOINC ®
14836-1
Performing Laboratory
Cleveland Clinic Laboratories
Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 1 mL | Plasma | Sodium or Lithium heparin (Green) | Centrifuge, aliquot and refrigerate. | Do not collect in a gel separator tube. Centrifuge and transfer plasma/serum to a CCL tube and refrigerate. |
Alternate Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 1 mL | Serum | No additive (Red) | Centrifuge, aliquot and refrigerate. | Do not collect in a gel separator tube. Centrifuge and transfer plasma/serum to a CCL tube and refrigerate. |
Minimum Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 0.5 mL |
Stability
| Environmental Condition | Description |
|---|---|
| Ambient | After separation from cells: 7 days capped |
| Refrigerated | After separation from cells: 14 days capped |
| Frozen | After separation from cells: 14 days capped |
Days Performed
Sun - Sat
Turnaround Time
8 hours
Methodology
| Name | Description |
|---|---|
| Enzyme Immunoassay (EIA) |
Reference Range
| Methotrexate | |||||
|---|---|---|---|---|---|
| Sex | Age From | Age To | Type | Range | Range Unit |
| 0.00 to 0.10 umol/L |
Special Info
The following values are predictive for the development of toxicity: -Methotrexate >5-10 µmol/L 24 hours after dose -Methotrexate >1.0 µmol/L 48 hours after dose -Methotrexate >0.1 µmol/L 72 hours after dose The treating physician must determine appropriate target levels/dosing based on the specific clinical situation. This result is not valid for patients who have received GLUCARPIDASE (carboxypeptidase G2) as a high dose rescue therapy. Alternative Methotrexate testing is available by send-out for patients on glucarpidase. References: ARK™ Methotrexate Assay [package insert 1600-0213-00 Rev 05]. ARK Diagnostics, Inc., Fremont, CA; Revised October 2014. Widemann, B.C., Adamson, P.C. (2006). Understanding and Managing Methotrexate Nephrotoxicity. The Oncologist, 11, 694-703.
Clinical Info
Monitor therapeutic use of methotrexate, high dose - determine need for marrow rescue