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T3, Reverse, LC/MS/MS : 90963
Test CodeT3RLCQ or 90963
Alias/See Also
RT3, Triiodothyronine Reverse, rT3, Reverse Triiodothyronine, Reverse T3, T3 Reverse
CPT Codes
84482
Instructions
Plain red, serum separator tube, green (no gel) (sodium heparin), or lavender (EDTA) tube.
Transport Container
Allow blood to clot at room temperature for 30 minutes. Centrifuge and separate the serum from cells within 24 hours of collection. Alternatively, collect blood in a gel barrier tube, allow to clot at room temperature, centrifuge and remove from gel within 24 hours. If green (no gel) sodium heparin or lavender (EDTA) tube, centrifuge to separate from cells within 24 hours of collection. After centrifugation immediately aliquot 0.5 mL (Min: 0.3 mL) serum or plasma into a standard transport tube.
Transport Temperature
Refrigerated.
Specimen Stability
Ambient: 7 days; Refrigerated: 7 days; Frozen: 30 days
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Unseparated serum or plasma, Serum in Serum Separator Tube (SST) not separated from the gel within 24 hours.
Methodology
Chromatography/Mass Spectrometry
Setup Schedule
Sunday - Saturday
Report Available
2-4 days (From receipt at performing laboratory)
Limitations
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.
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 (DIT) 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.
Performing Laboratory
Quest Diagnostics