Immunoassay of alpha 1-acid glycoprotein in the Cobas Bio centrifugal analyzer

There is an increasing demand for quantification of serum alpha 1-acid glycoprotein (AAG, orosomucoid) in studies evaluating the protein binding of highly bound basic drugs. This paper describes an adaptation of an automated immunoturbidimetric assay for this protein to the Cobas Bio centrifugal analyzer. Replicate analyses of aliquots from six different solutions were used in determining precision. We also analyzed 367 patients' serum samples, in duplicate, to determine the distribution of AAG in hospitalized patients. The intra- and inter-run CVs ranged from 1.3% to 4.4% and from 0.6% to 6.6%, respectively. AAG concentrations in patients' samples ranged from 0.38 to 3.16 g/L. Results by this method correlate well with those by radial immunodiffusion, with no significant amount of bias between the two methods. This immunoturbidimetric procedure is faster and less expensive than currently used radial immunodiffusion techniques, and precision is acceptable.