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Leflunomide Metabolite (Southeast Michigan Only)

Teriflunomide, Arava, Aubaigo

Test Codes

EPIC: LAB1231257, Beaker: LEFI, ARUP: 2007460

Department

Send Outs

Specimen Collection Criteria

Collect (preferred specimen): One plain Red-top tube.

Also acceptable: One Lavender-top EDTA tube, Pink-top K₂EDTA, Green-top Heparin or Gray-top Sodium Floride.

Physician Office/Draw Specimen Preparation

Timing of specimen collection: Predose (trough). Obtain specimen 12-24 hours after last dose.

Separate from cells within 2 hours of draw. Transfer 1 mL serum or plasma to a Transport Tube. (Minimum 0.2 mL)

Preparation for Courier Transport

Transport: Refrigerated (2-8°C or 36-46°F). (Minimum: 0.2 mL serum or plasma)
Also Acceptable:  Room temperature or frozen.

Rejection Criteria

Whole blood. Potassium Oxalate or Serum Separator (SST) tubes.

In-Lab Processing

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

Storage

Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): 7 days
Refrigerated (2-8°C or 36-46°F): 17 days
Frozen (-20°C/-4°F or below): 3 months

Laboratory

Sent to ARUP Laboratories, Salt Lake City, UT.

Performed

Sunday, Wednesday, Friday.
Results available in 1-6 days.

Reference Range

Therapeutic Range: >40.000 µg/mL.

Test Methodology

High Performance Liquid Chromatography/Mass Spectrometry (LC/MS/MS).

Interpretation

Therapeutic and toxic ranges are not well established. Concentrations greater than 40.000 µg/mL tend to correlate with improved patient outcome. A proposed therapeutic range is 50.000 – 100.000 µg/mL. Adverse reactions to Leflunomide, such as diarrhea, hypertension, and liver toxicity, do not correlate well with serum drug concentrations. Leflunomide has a potential risk for teratogenesis. For women being treated with Leflunomide who desire to become pregnant, enhanced drug elimination should be performed until plasma teriflunomide concentrations are lower than 0.020 µg/mL on two separate tests taken at least 14 days apart. This test was developed, and its performance characteristics determined by ARUP Laboratories. It has not been cleared or approved by the US Food and Drug Administration. This test was performed in a CLIA certified laboratory and is intended for clinical purposes. Compliance Category: Laboratory Developed Test (LDT)

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 Codes

80193
LOINC:  Teriflunomide 44828-2

Contacts

Last Updated

11/4/2024