Free T4
Abbreviation
FT4
Preferred Specimen
Serum
Minimum Volume
0.5mL
Collection Instructions
Routine Venipuncture
Transport Container
Draw tube or plastic pour off tube
Transport Temp
2-8C
Stability
- 2-8 C for 48 hours
- -20C up to 12 months
Methodology
CLIA (chemiluminescent immunoassay)
Reference Ranges
0.29-7.7 ng/mL
Clinical Significance
FT 4 should be determined in the following binding protein anomalies: congenital (familiar dysalbuminaemic, hyperthyroxinaemia, pre-albumin-associated hyperthyroxinaemia, congential TBG deficiency); physiological (pregnancy, perinatal state); drug-related (contraceptives, salicylates, heparin); NTI-non-thyroidal illness (chronic renal insufficiency, myocardial infarction, acute hepatitis, hepatic cirrhosis, anorexia nervosa, severe infections, postoperative and posttraumatic states). FT4 distinguishes euthyroid hyperthyroxinaemias from hyperthyroidism and euthyroid hypothyroxinaemias from hypothyroidism