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Test Code 0232355 T3 (Triiodothyronine), Reverse, Serum

Additional Codes

 

Mayo Test ID
RT3

 

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Useful For

An aid in the diagnosis of the "sick euthyroid" syndrome

Method Name

Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)

Portions of this test are covered by patents held by Quest Diagnostics.

Reporting Name

T3 (Triiodothyronine), Reverse, S

Specimen Type

Serum


Specimen Required


Collection Container/Tube:

Preferred: Red top

Acceptable: Serum gel

Submission Container/Tube: Plastic vial

Specimen Volume: 0.8 mL


Specimen Minimum Volume

0.4 mL

Specimen Stability Information

Specimen Type Temperature Time
Serum Refrigerated (preferred) 28 days
  Ambient  28 days
  Frozen  28 days

Reject Due To

Hemolysis

Mild OK; Gross reject

Lipemia

Mild OK; Gross OK

Icterus

Mild OK; Gross OK

Other

NA

Reference Values

10-24 ng/dL

Interpretation

In hospitalized or sick patients with low triiodothyronine (T3) values, elevated reverse triiodothyronine (rT3) values are consistent with "sick euthyroid" syndrome. Also, the finding on an elevated rT3 level in a critically ill patient helps exclude a diagnosis of hypothyroidism.

 

The rT3 is high in patients on medications such as propylthiouracil, ipodate, propranolol, amiodarone, dexamethasone, and the anesthetic agent halothane. Dilantin decreases rT3 due to the displacement from thyroxine-binding globulin, which causes increased rT3 clearance.

 

To convert from ng/dL to nmol/L, multiply the ng/dL result by 0.01536.

Day(s) and Time(s) Performed

Monday, Wednesday, Thursday, Friday; 9 a.m.

Analytic Time

2 days

Specimen Retention Time

14 days

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

84482

LOINC Code Information

Test ID Test Order Name Order LOINC Value
RT3 T3 (Triiodothyronine), Reverse, S 3052-8

 

Result ID Test Result Name Result LOINC Value
9405 T3(Triiodothyronine),Reverse,S 3052-8

Forms

If not ordering electronically, complete, print, and send a General Request (T239) with the specimen.