Kinetic immunoturbidimetric measurement of thyroxine binding globulin.

We describe the extension of kinetic immunoturbidimetry to measurement of low-concentration proteins in serum, specifically thyroxine binding globulin. Method performance is superior to that of currently available direct assays for this protein by radioimmunoassay or the Laurell "rocket" techniques. The assay is rapid (1-min measurement period), economical, and results compare well with those by established techniques. The technique has wide applicability to instruments with kinetic measuring ability and could provide a useful support to other non-isotopic thyroid-function tests. The assay further emphasizes the sensitivity and usefulness of kinetic immunoturbidimetry for measuring low concentrations of proteins.