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Test Code LAB481 Methotrexate, Serum

Additional Codes

Mayo Test Code: MTHX

Useful For

Following therapy, serum concentration is used to judge whether the drug is being cleared appropriately and verify that a nontoxic concentration has been attained

Method Name


Reporting Name

Methotrexate, S

Specimen Type


Specimen Required

Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Amber vial (T192)

Specimen Volume: 0.5 mL

Collection Instructions:

1. Serum gel tubes should be centrifuged within 2 hours of collection.

2. Red-top tubes should be centrifuged and aliquoted within 2 hours of collection.

3. Send specimen in amber vial to protect from light.

Specimen Minimum Volume

0.25 mL

Specimen Stability Information

Specimen Type Temperature Time
Serum Refrigerated (preferred) 14 days
  Frozen  28 days
  Ambient  72 hours

Reject Due To


Mild OK; Gross reject







Reference Values

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

Performing Laboratory

Mayo Medical Laboratories in Rochester

Test Classification

This test has been cleared or approved by the U.S. Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
MTHX Methotrexate, S 14836-1


Result ID Test Result Name Result LOINC Value
MTHX Methotrexate, S 14836-1

Day(s) and Time(s) Performed

Monday through Sunday; Continuously