Beaumont Laboratory - Lab Test Details

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Beaumont Laboratory

Leflunomide Metabolite

Teriflunomide, Arava, Aubaigo, EPIC: LAB6787, SOFT: LEFI

Specimen Collection Criteria

Collect (preferred specimen): One plain Red-top tube.
Also acceptable: One Green-top Heparin or Lavender-top EDTA tube.

Do not use Serum Separator Tubes. 

Physician Office/Drawsite Specimen Preparation

Let serum specimens clot 30-60 minutes. Centrifuge specimen to separate serum or plasma from cells. Refrigerate (2-8°C or 36-46°F) the centrifuged collection tube within two hours of collection. (Min: 0.2 mL serum or plasma)

Preparation for Courier Transport

Transport: Centrifuged collection tube, refrigerated (2-8°C or 36-46°F). (Min: 0.2 mL serum or plasma)

Rejection Criteria

  • Serum Separator (SST) tubes.


Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): 2 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:

Frozen (-20°C/-4°F or below): 2 months


Royal Oak Toxicology Laboratory.


Tuesday, Friday.
Results available the same day as testing performed (1-4 days).

Reference Range

Therapeutic Range: 30-60 mcg/mL.
Critical Range: Greater than 100 mcg/mL. 

Test Methodology

Liquid Chromatography/Tandem Mass Spectrometry (LC/MS/MS).

This test was developed and its performance characteristics determined by Beaumont Health. It has not been cleared or approved by the FDA. The Laboratory is regulated under CLIA as qualified to perform high-complexity testing. This test is used for clinical purposes and should not be regarded as investigational or for research.


Teriflunomide is the active metabolite of the pro-drug Leflunomide. Leflunomide is used as an alternative therapy to Methotrexate in rheumatoid arthritis and in transplantation as an anti-viral drug in treatment for BK Virus Nephropathy. Leflunomide is both an immunosuppressant and inhibits viral replication. Suggested therapeutic targets must be correlated with severity of infection, patient response, and co-medications. Higher serum concentrations are associated with hemolysis, anemia, thrombotic microangiography and hepatotoxicity. Teriflunomide is eliminated very slowly with a half life averaging 15 days. Teriflunomide is highly protein bound (99.5%) and aging, renal disease, and concomitant medication such as Warfarin, Salicylates, Valproic Acid, and Phenytoin may increase the percent of unbound drug.

Clinical Utility

This assay is used to monitor the therapeutic drug level and evaluate the risk of toxicity of the active metabolite of Leflunomide.

CPT Code

80375 (alternate: G0480).

Test Codes


Last Updated


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This directory currently reflects information only for specimens collected and/or processed at the Farmington Hills, Grosse Pointe, Royal Oak, and Troy campuses.