A novel method for the detection of variation in solid-phase immobilised antibody concentration and its possible...

Variation of solid-phase antibody concentration could give rise to poor intra- and interassay precision. A new method to detect this variation is reported. Pooled sera with thyroxine (T4) values at the low, medium, and high ranges were assayed in duplicate using anti-T4-coated polystyrene beads. The antigen-antibody complexes were dissociated with methanol-water mixture and the antibodies re-used for subsequent T4 assays in which the same beads were used with the same set of standards and pooled sera. A second set of assays using randomised beads after each assay-wash cycle were also carried out. The variations in weights and surface structures of the beads were also studied. The variation of T4 results of group methods using polyethylene glycol in an external quality control program was also compared with that of covalently linked solid-phase particulate antibody methods over 2 periods. The experimental results showed that there was bead-to-bead variation of antibody concentration which could give rise to poor precision. Rigorous control of the immobilised antibody concentration could further improve the assay performance.