A SIMPLE, AUTOMATED, NONEXTRACTION ASSAY FOR SERUM DIGOXIN USING PARTICLE-ENHANCED IMMUNOASSAY

We have adapted a latex particle-enhanced immunoassay for serum digoxi n to a centrifugal analyser. A 4-mu l serum sample (without pretreatme nt) inhibits the monoclonal antibody induced aggregation of digoxin-co ated latex particles. The total assay time is 10 min and mean analytic al recoveries were 98.1%. Intra and interassay precision were < 4.2 an d < 15.0%, respectively. Method comparison with an established fluores cence polarisation immunoassay (FPIA) gave R = 0.97, and a Deming regr ession analysis of particle-enhanced turbidimetric inhibition immunoas say (PETINIA) = FPIA x 0.78 + 0.007 mu g/L (n = 91). There was no evid ence of significant interference from digoxin-like immunoreactive comp ounds in patients with chronic renal failure. This assay can be adapte d to most photometric analysers used in routine laboratories and is a significant advance in the sensitivity of latex particle-enhanced immu noassays in a serum matrix.