title: Automated and manual serum free thyroxine assays evaluated with equilibrium dialysis.
abstract: Two fully automated serum FT4 assays (Ciba Corning: ACS-180; Abbott Diagnostics: IMx) and two manual/semiautomated assays (Wallac: Delfia; Diagnostic Products Corp.: Coat-A-Count) were compared with a FT4 reference method based on equilibrium dialysis (ED) using routine clinical samples (n = 105-150). For the full range of FT4 concentrations the correlation with ED was good (r = 0.932-0.959), except for Coat-A-Count (r = 0.852), a single-step analogue-type method. Analytical inaccuracy of the automated methods at low FT4 concentrations was revealed by the differential plot: the IMx assay overestimated concentrations < 10 pmol l-1 and the ACS-180 assay concentrations < 6 pmol l-1. The between-assay CVs for the automated methods were not better than for the non-automated assays indicating problems of calibration curve stability for the automated assays.
authors.affiliation: Department of Clinical Chemistry, University of Helsinki, Finland.
authors.forename: K
authors.initials: K
authors.lastname: Liewendahl
authors.forename: L
authors.initials: L
authors.lastname: Melamies
authors.forename: T
authors.initials: T
authors.lastname: Helenius
authors.forename: S L
authors.initials: SL
authors.lastname: Karonen
authors.forename: E
authors.initials: E
authors.lastname: Liljeström
authors.forename: M
authors.initials: M
authors.lastname: Välimäki
authors.forename: T
authors.initials: T
authors.lastname: Weber
mesh_terms: D001322:Autoanalysis; D003956:Dialysis / Q000379:methods; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D008163:Luminescent Measurements; D012680:Sensitivity and Specificity; D013974:Thyroxine / Q000097:blood*
chemical_list: D013974:Thyroxine