Simplified technic for the determination of serum protein-bound iodine.

A simplified technic for the determination of serum protein-bound iodine (PBI) is presented. Endogenouslylabeled 1131 PBI is completely recovered. The technic is basedon the method of Barker et al. (1) and includes the following modifications: The number of washesof the precipitated serum proteins are decreased. Unashed iodide standards are used in a sodium carbonate solution rather than an internal standard. A temperature-correction formula is employed to allow the cericarsenite-iodide reaction to be carried out at room temperature, and a stable cerate color is producedwith brucine sulfate so that the colorimetry is carried out with greater convenience. The serum PBI concentrations are read directly from a graph, which simplifies the calculations.