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T3 Reverse, LC/MS/MS
Test Code90963
CPT Codes
84482
Preferred Specimen
0.5 mL serum
Minimum Volume
0.3 mL
Other Acceptable Specimens
Plasma collected in sodium heparin (green-top), or EDTA (lavender-top) tube
Instructions
Serum: Allow blood to clot at room temperature for 30 minutes. Centrifuge to separate serum from the cells within 24 hours of collection and immediately pour serum into a plastic transport tube.
Plasma: Centrifuge to separate plasma from the cells within 24 hours of collection and immediately pour plasma into a plastic transport tube.
Transport Container
Transport tube
Transport Temperature
Room temperature
Specimen Stability
Room temperature: 7 days
Refrigerated: 7 days
Frozen: 30 days
Refrigerated: 7 days
Frozen: 30 days
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Unseparated serum (>48 hours on clot) • Serum in Serum separator tube (SST) not separated from the gel within 24 hours
Methodology
Chromatography/Mass Spectrometry
FDA Status
This test was developed and its analytical performance characteristics have been determined by Quest Diagnostics. It has not been cleared or approved by FDA. This assay has been validated pursuant to the CLIA regulations and is used for clinical purposes.
Setup Schedule
Set up: Daily; Report available: 2-4 days
Reference Range
8-25 ng/dL
Clinical Significance
3,3',5'-Triiodothyronine (reverse T3, rT3) is, along with 3,3,5'-Triiodothyronine (T3) a deiodinated metabolite of thyroxine (T4), the major secretory product of the thyroid gland and is secreted into the bloodstream. Unlike T3, however, rT3 is thought to be metabolically inert.
The process of 5'-monodeiodination that converts T4 to T3, and rT3 to diiodothyronine (DTT) is inhibited in a wide variety of conditions, collectively referred to as nonthyroidal illnesses (NTI) or the 'euthyroid sick' state. These conditions include fasting, malnutrition, poorly controlled diabetes mellitus, trauma, surgery, and systemic illness. Consequently, in patients with NTI the serum T3 level typically decreases, and the rT3 often, but not always, increases.
The process of 5'-monodeiodination that converts T4 to T3, and rT3 to diiodothyronine (DTT) is inhibited in a wide variety of conditions, collectively referred to as nonthyroidal illnesses (NTI) or the 'euthyroid sick' state. These conditions include fasting, malnutrition, poorly controlled diabetes mellitus, trauma, surgery, and systemic illness. Consequently, in patients with NTI the serum T3 level typically decreases, and the rT3 often, but not always, increases.
