Triiodothyronine, Total, serum and plasma

Alternate test name

Total T3

Lab area

Clinical Biochemistry - General

Method and equipment

Equipment : Roche Cobas Pro e801

Method : Competition principle. Total duration of assay: 18 minutes.
▪ 1st incubation: 18 µL of sample and a T3‑specific antibody labeled with a ruthenium complex; bound T3 is released from the binding proteins in the sample by ANS.
▪ 2nd incubation: After addition of streptavidin-coated microparticles and biotinylated T3, the still-free binding sites of the labeled antibody become occupied, with formation of an antibody-hapten complex. The entire complex becomes bound to the solid phase via interaction of biotin and streptavidin.
▪ The reaction mixture is aspirated into the measuring cell where the microparticles are magnetically captured onto the surface of the electrode. Unbound substances are then removed with ProCell II M. Application of a voltage to the electrode then induces chemiluminescent emission which is measured by a photomultiplier.

Results are determined via a calibration curve which is instrument specifically generated by 2‑point calibration and a master curve provided via the cobas link.

Expected turn-around time

STAT: 24 Hours Urgent: 24 Hours Routine: 24 Hours

Specimen type

Serum or Plasma Lithium Heparin

Specimen requirements

150 uL

Storage and transportation

Frozen

Shipping information

The Hospital for Sick Children

Rapid Response Laboratory

555 University Avenue, Room 3642

Toronto, ON

Canada

M5G 1X8

Phone: 416-813-7200

Toll Free: 1-855-381-3212

Hours: 7 days/week, 24 hours/day

Requisition

Triiodothyronine, Total, serum and plasma - requisition

Background and clinical significance

3,5,3’ Triiodothyronine (T3) is a thyroid hormone with a molecular weight of 651 daltons and a half-life in serum of 1.5 days. T3 circulates in the blood as an equilibrium mixture of free and protein bound hormone. T3 is bound to thyroxine binding globulin (TBG), prealbumin, and albumin It has become apparent in recent years that T3 plays an important role in the maintenance of the euthyroid state. Serum T3 measurements can be a valuable component of a thyroid screening panel in diagnosing certain disorders of thyroid function as well as conditions caused by iodine deficiency. Clinically, measurements of serum T3 concentration are especially valuable in diagnosing hyperthyroidism and in following the course of therapy for this disorder.