Equilibrium Dialysis
Also written as: ED — Equilibrium Dialysis
A reference method for measuring free hormone fractions by physically separating bound from unbound hormone through selective membrane diffusion.
Full Definition
Equilibrium dialysis is a reference laboratory technique used to determine the free (unbound) fraction of protein-bound hormones by allowing equilibrium to establish across a semipermeable membrane. The method involves placing serum samples in dialysis chambers where only free hormone molecules can cross the membrane, while protein-bound hormones remain on the original side. After equilibrium is reached, the concentration of hormone that has crossed the membrane represents the true free fraction. This technique is particularly important for measuring free testosterone, free cortisol, and free thyroid hormones, providing definitive results when binding protein abnormalities or assay interferences are suspected. While time-consuming and labor-intensive, equilibrium dialysis serves as the gold standard against which other free hormone methods are validated.
Usage
Usage note: Considered the reference method for free hormone determination but not widely available in routine practice.
In Context
- "Equilibrium dialysis confirmed the free testosterone result when binding protein abnormalities were suspected." — Reference laboratory report
- "The discordant free T4 results necessitated confirmation by equilibrium dialysis methodology." — Endocrinology consultation