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T3 (Triiodothyronine) Reverse

Order Name REVERSE T3
Test Number: 2010900
Revision Date 08/01/2017
Test Name Methodology LOINC Code
T3 (Triiodothyronine) Reverse
Liquid Chromatography/Tandem Mass Spectrometry 3052-8 
Specimen Specimen Volume (min) Specimen Type Specimen Container Transport Environment
Preferred 2 mL (1 mL) Serum Clot Activator SST Frozen
Alternate 1 2 mL (1 mL) Plasma EDTA (Lavender Top) Frozen
Instructions Allow serum specimen to clot completely at room temperature.
Separate serum or plasma from cells ASAP or within two hours of collection.
Unacceptable Conditions: Grossly hemolyzed specimens

Stability after separation from cells/gel: Ambient: 24 hours; Refrigerated: 1 week; Frozen: 3 months
Testing Schedule Sun-Sat 
Expected TAT 2-5 Days  
Clinical Use Reverse T3 (rT3) has limited application. The assay may be useful in the diagnosis of nonthyroidal illness (NTI). Patients with NTI have low T3 concentrations and increased concentrations of rT3. RT3 may be useful in neonates to distinguish euthyroid sick syndrome from central hypothyroidism. 
CPT Code(s) 84482
Lab Section Reference Lab