Triiodothyronine (T3, Total)
Test name: Triiodothyronine (T3, Total)
Order Code: T3
Preferred Specimen: 2mL serum in a Serum Separator Tube (SST or Tiger-top)
CPT Code: 84480
Collection: Allow SST to clot in an upright position for 30 min, then centrifuge sample within 2 hours of collection. Refrigerate.
Special Instructions and Considerations: Samples should not be taken from patients receiving therapy with high biotin doses (i.e. > 5 mg/day) until at least 8 hours following the last biotin administration. Therapy with amiodarone can lead to depressed T3 values. Phenytoin, phenylbutazone, and salicylates cause release of T3 from the binding proteins, thus leading to a reduction in the total T3 hormone level at normal free T3 levels. Autoantibodies to thyroid hormones can interfere with the assay. Binding protein anomalies seen with FDH (familial dysalbuminemic hyperthyroxinemia), for example, may cause values which, while characteristic of the condition, deviate from the expected results. Pathological concentrations of binding proteins (TGB, albumin) can lead to total T3 values outside the normal range being found despite a euthyroid metabolic state (e.g. in NTI-patients, pregnancy, use of oral metabolic contraceptives). In such cases a free T3 or free T4 determination is indicated.
Transport Temperature: Refrigerated
Specimen Stability: 7 days refrigerated