Three immunoassay methods evaluated for quantifying prealbumin (transthyretin) in serum.

We developed an immunoturbidimetric assay for prealbumin on the Cobas Bio centrifugal analyzer and compared results from this assay with those from a rate nephelometric assay (Beckman Instruments Inc.) and a radial immunodiffusion kit (Behring Diagnostics). All three assays were evaluated for precision, linearity, and correlation to each other for analysis of sera from pediatric patients. All assays gave similar results for patients' samples. Values were higher by the radial immunodiffusion assay than by the other two methods, which gave similar results for the same specimens. We conclude that the immunoturbidimetric and rate nephelometric assay for prealbumin are acceptable alternatives for quantifying prealbumin in serum and also have a faster turnaround time than radial immunodiffusion.