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Methotrexate Level, Serum

Mexate

Test Codes

EPIC: LAB5403, MTX

Department

Chemistry

Specimen Collection Criteria

Collect: One plain Red-top tube. (Minimum Whole Blood: 2.0 mL)

• Protect specimen from light.
• Do not use Serum Separator Tubes.
• Time of Collection: Follow protocol requirements.
• Record the exact time of specimen collection on the tube or in the computer system.

Physician Office/Draw Specimen Preparation

Protect specimen from light. Let specimens clot 30-60 minutes. Centrifuge specimen to separate serum from cells. Refrigerate (2-8°C or 36-46°F) the centrifuged collection tube within two hours of collection. (Minimum: 0.5 mL serum)

Preparation for Courier Transport

Transport: Light-protected centrifuged collection tube, refrigerated (2-8°C or 36-46°F). (Minimum: 0.5 mL serum)

Rejection Criteria

• Serum Separator (SST) tubes.
• Severely lipemic or hemolyzed specimens.  

In-Lab Processing

Protect specimen from light. Let specimens clot 30-60 minutes. Centrifuge specimen to separate serum from cells. Deliver immediately to the appropriate testing station.

Storage

Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): 24 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): 3 months

Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): 7 days

Laboratory

Royal Oak STAT Laboratory

Performed

Sunday – Saturday, 24 hours a day.
STAT results available within 1 hour of receipt in the Laboratory.
Routine results available within 24 hours. 

Reference Range

Concentrations greater than 1.0 mcM/L after 48 hours may indicate toxicity and warrant antidote intervention.

Test Methodology

Enzyme Immunoassay.

Interpretation

Methotrexate is administered by iv injection in high dose protocols and must be monitored regularly to assess the need for leucovorin rescue.

Clinical Utility

This assay is used to monitor the therapeutic drug level and evaluate the toxicity of methotrexate. Methotrexate is an antineoplastic agent. It is used in the treatment of malignancies with rapid cell proliferation such as acute lymphoblastic leukemia, choriocarcinoma, trophoblastic tumors in women, and carcinomas of the breast, tongue, pharynx, and testis. It is also indicated in the treatment of severe psoriasis and adult rheumatoid arthritis.

CPT Codes

80375 (alternate: G0480).
LOINC: 14836-1

Contacts

Last Updated

1/19/2022