Test Overview

Test Methodology

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

Test Usage

Therapeutic Drug Monitoring

Reference Range*

Therapeutic: >40 mcg/mL; Elimination:

* Reference ranges may change over time. Please refer to the original patient report when evaluating results.

Test Details

Days Test Performed

Monday, Wednesday, Friday

Analytic Time

3 - 7 days

Soft Order Code


MiChart Code

Leflunomide Metabolite Serum (Sendout)




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Laboratory Reference

Mayo LEFLU (60292)

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Specimen Requirements

Offsite Collection Instructions

Collect specimen in a red top (preferred) or SST tube. Centrifuge and aliquot serum into a plastic vial within 2 hours of collection. Store and transport at room temperature (preferred); specimen may be stored refrigerated or frozen for up to 14 days.


Red Top Tube

Normal Volume

1 mL serum

Minimum Volume

0.3 mL serum

Additional Information

Test sent to Mayo Medical Laboratories.

Billing Information

Fee Codes

CPT Code


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