Concentration of thyroxine-binding globulin: value of direct assay.
The concentration of thyroxine-binding globulin (TBG) in the serum can now be measured by direct assays that are simple and inexpensive. Comparison of a direct measurement of TBG concentration with a widely used indirect method (Thyopac-3) showed that the indirect method was inaccurate when TBG concentrations were high. This will result in an increase in the derived free thyroxine index (FTI), so that euthyroid patients with a raised TBG concentration may be at risk of being labelled thyrotoxic. Correction of serum total thyroxine (T4) concentration according to the actual TBG concentration (T4:TBG ratio) provided a better correlation with thyroid state than FTI.
D000293:Adolescent; D000328:Adult; D000510:Alpha-Globulins / Q000032:analysis*; D005260:Female; D006801:Humans; D007122:Immunoelectrophoresis / Q000379:methods; D008297:Male; D008875:Middle Aged; D011863:Radioimmunoassay; D013959:Thyroid Diseases / Q000235:genetics; D013975:Thyroxine-Binding Proteins / Q000032:analysis*
D000510:Alpha-Globulins; D013975:Thyroxine-Binding Proteins