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Test Code BLOD1106 Leflunomide Metabolite (Teriflunomide), Serum

Additional Codes

Mayo Test Code: LEFLU

Useful For

Therapeutic monitoring of patients actively taking leflunomide


Assessment of elimination in patients requiring enhanced elimination of the drug

Performing Laboratory

Mayo Medical Laboratories in Rochester

Specimen Type

Serum Red

Specimen Required

Collection Container/Tube:

Preferred: Red top

Acceptable: Serum gel

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL

Collection Instructions:

1. Draw blood no sooner than 12 hours (trough value) after last dose.

2. Spin down within 2 hours of draw.

Specimen Minimum Volume

0.3 mL

Specimen Stability Information

Specimen Type Temperature Time
Serum Red Ambient (preferred) 28 days
  Frozen  28 days
  Refrigerated  28 days

Reference Values

Therapeutic: >40 mcg/mL

Elimination: <0.020 mcg/mL

Day(s) and Time(s) Performed

Monday, Wednesday, Friday; 4 p.m.

Test Classification

This test has been modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information


Reject Due To


Mild OK; Gross OK


Mild OK; Gross OK


Mild OK; Gross OK



Method Name

High-Turbulence Liquid Chromatography Mass Spectrometry (HTLC-MS/MS)