Free thyroid hormones in serum by direct equilibrium dialysis
and online solid-phase extraction--liquid chromatography/tandem mass spectrometry.
The patent issued to Harvard Bioscience is for an equilibrium dialysis
system that enables samples to be prepared simultaneously in multiples.
Use of frozen sera for FT4 standardization: investigation by equilibrium dialysis
combined with isotope dilution mass spectrometry and immunoassay.
4] from the sample and replaces the dialysis step of the classic equilibrium dialysis
Many attempts have been made to resolve the debate by applying methods based on ultrafiltration and equilibrium dialysis
in combination with direct quantification of the separated FTHs (2, 17).
This was done to provide the endocrinologists at Children's National Medical Center with results that were essentially identical to those obtained by the then gold standard equilibrium dialysis
immunoassay (EDIA) method marketed by Nichols.
4] measured by equilibrium dialysis
(EDFT4) was within the reference interval (Table 1).
In the field of free thyroid hormone testing, methods based on equilibrium dialysis
(ED) or ultrafiltration (UF) of serum, before direct measurement of the hormone concentration in the dialysate or ultrafiltrate, are accepted to be gold standards (1).
Theoretically, both equilibrium dialysis
(ED) and ultrafiltration (UF) can be valid methodologies.
It is of note that the reference interval for free T by analog-based assay is much lower (concentrations about one-fifth as high) than that for the equilibrium dialysis
1) during equilibrium dialysis
at 37 [degrees]C by HEPES acid in the dialysate buffer (14).
Finally, although ultrafiltration, equilibrium dialysis
, and direct analog assays have the same aims, in regard to sampling and dilution these different assays represent opposite ends of a spectrum of valid methods.