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