A routine method for the estimation of serum protein-bound iodine.

A method for the determination of serum protein-bound iodine (PBI) is presented. Chioric acid digestion is carried out in a single tube as described by other authors. In order to shorten the period when close supervision is necessary, the digestion process has been reduced to 1 hour and the estimation completed within 4 hours. The method has been modified to make it a more manageable routine procedure for either single or multiple estimations of PBI. To overcome complications involved in temperature control, the final estimation of inorganic iodide by the catalytic reduction of Ce+4 to Ce+3 is carried out at room temperature. The value of this method as a thyroid function test is assessed in 125 cases.