A regional external quality assessment scheme for serum thyroxine-binding globulin

The results from a Regional External Quality Assessment Scheme for the assay of serum thyroxine binding globulin (TBG) are presented. It has been shown that different methods of analysis (eg, rocket immuno-electrophoresis, radioimmunoassay, and radial immunodiffusion) produce comparable results using a common calibrant. Since there is no commonly agreed universal calibrant for TBG, however, results (in mg/l) for various assay systems with differing methods of calibration show wide variance.