Test Code: 4022CPT: 84479
|Use||Used to asses the thyroxine-binding capacity of unsaturated proteins in serum and plasma and may also be used in conjunction with a total thyroxine measurement to provide a calculated free thyroxine index (FTI).|
|Clinical Utility||In hypothyroidism the relatively unsaturated binding proteins reflect a decreased thyroid uptake value. In hyperthyroidism the thyroid uptake value increases due to the highly saturated binding proteins|
|Intended Patient Population||18+ and Older Adult Males & Females|
|Patient Preparation||None Specified|
|Tube||Red, Green, Tiger|
|Volume||4mL Whole Blood (1mL Serum/Plasma)|
|Min Sample Volume||0.5 mLs|
|Reference Ranges||NEED TO FIND OUT|
|Analytical Measurement Range||N/A|
|Test Methodology||Chemiluminescent Immunoassay|
|Test Turnaround Time||2 Days|
|Limitations||In addition to thyrometabolic disorders, the following can alter the thyroid uptake value in euthyroid individuals:1,2
Increased Thyroid Uptake: Reduced TBG synthesis (androgens or anabolic steroids), Hypoproteinemia (nephrosis, malnutrition), Drugs (Phenytoin, salicylates), Extrathyroidal disease (hepatic disease, generalized illness, acromegaly), and Hereditary TBG deficiency.
Decreased Thyroid Uptake: Increased TBG synthesis (pregnancy, estrogen administration, oral contraceptives), Hyperproteinemia, Drugs (prolonged phenothianzine administration), Extrathroidal disease (hepatic disease), Hereditary TBG excess.
|Specimen Stability||7 Days RF|
|Reject Criteria||Gross Hemolysis|
|Laboratory Developed Test (LDT)||Yes|
|CMS Guidance||NCD 190.22|
|References||1. Gornall, AG, Luxton, AW, Bhavnani, BR. Endocrine disorders. In Applied Biochemistry of Clinical Disorders, 1986; 305-318. Edited by Gornall, A.G. Philadelphia, PA: J. B. Lippincott Co.
2. White, GH. Recent advances in routine thyroid function testing. CRC - Critical Reviews in Clinical Laboratory
Sciences, 1987, 24: 315-362.