T3 Reverse, LC/MS/MS
Also known as: Reverse T3, Reverse Triiodothyronine, RT3, rT3, Triiodothyronine Reverse
Use
Reverse triiodothyronine (rT3) is measured to assess thyroid hormone metabolism—particularly in the evaluation of sick euthyroid syndrome or other conditions affecting peripheral conversion of thyroid hormones, such as nonthyroidal illness. Abnormal rT3 levels may indicate altered deiodinase activity or adaptive metabolic responses.
Special Instructions
Portions of this test are covered by patents held by Quest Diagnostics. Send‑out specialty test; requires red‑top or EDTA/heparin plasma collection, separation, and timely handling to ensure validity.
Limitations
Specimens must be properly processed: unseparated serum for >48 hours on clot or serum separated after 24 hours in SST tube may lead to rejection. Clinical interpretation may be limited in hospitalized or acutely ill patients where rT3 elevation may be nonspecific.
Methodology
Mass Spectrometry
Biomarkers
Result Turnaround Time
5-6 days
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
0.5–2 mL blood (yields ~0.5 mL serum)
Minimum Volume
0.3 mL
Container
Red‑top tube (no additive); EDTA (lavender) or sodium heparin (green) plasma acceptable
Collection Instructions
Allow blood to clot at room temperature for 30 minutes; centrifuge and separate serum immediately, or if using SST, remove from gel within 24 hours; plasma alternate tubes similarly processed.
Causes for Rejection
Unseparated serum >48 hours on clot; serum in SST not separated from gel within 24 hours
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 7 days |
| Refrigerated | 7 days |
| Frozen | 30 days |