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Alias Names: Thyroxine / FT4 Dialysis
Methodology: Immunochemiluminometric Assay/Dialysis/ Radioimmunoassay (ICMA/D/RIA)
Edit Date: 11/13/2008
Performed: Tuesday, Friday
Released: 3-7 days after setup at PeaceHealth Laboratories’ reference lab
CPT Code: 84439-90
Specimen Collection Details
Collection: One 7.5 mL serum separator tube (SST).
Handling: Centrifuge and separate serum from cells and pour into a plastic vial. Freeze.
Stability: 1 hour ambient, 4 days refrigerated, or 2 months frozen.
Standard Volume: 1 mL serum.
Minimum Volume: 0.5 mL serum.
Transport: Frozen on dry ice.
Comments: T4 and T3 circulate in the blood as equilibrium mixtures of free and protein-bound hormones. Changes in concentration or affinity of TBG or other transport proteins profoundly affect the total hormone concentration in serum. The free hormone is independent of these binding protein variations and remains almost constant. Direct dialysis is an equilibrium dialysis method in which undiluted serum specimens are dialyzed for 16-18 hours at 37° C in a reusable dialysis chamber. The dialysis buffer provides for minimal changes in the serum matrix. The dialysate is then analyzed directly using a sensitive immunoassay.

PeaceHealth Laboratories