title: Comparative evaluation of digoxin concentrations determined by three assay systems: TDx, IMx and OPUS.
abstract: Digoxin concentrations measured by three automated immunoassay systems, i.e. OPUS, TDx and IMx assays, were compared in order to evaluate precision and accuracy performance, and data compatibility. Coefficients of variation for all methods in within-run and between-run precision were less than 10% at weighed-in concentrations of 0.545, 1.090 and 2.180 ng/ml. The accuracy relative to the three weighed-in concentrations ranged from 97% to 123% for all methods. One hundred and three plasma samples from 60 patients receiving digoxin were used to evaluate the data compatibility. Digoxin concentrations measured by the three immunoassay systems correlated well with one another. These results suggest that there are few problems when switching between digoxin assay methods, and that IMx and OPUS are more useful than TDx because they do not require sample pretreatment. The digoxin concentrations of the plasma samples from one patient receiving both digoxin and potassium canrenoate were investigated as a case report. The digoxin concentrations measured by TDx and IMx became higher than those measured by OPUS after starting the combination treatment. In another patient suffering from bilirubinaemia, the digoxin concentrations measured by TDx or IMx were higher than those measured by OPUS. These results suggest that OPUS has a higher specificity for measuring the plasma digoxin concentrations compared with TDx or IMx.
authors.affiliation: Department of Hospital Pharmacy, Mie University School of Medicine, Edobashi 2-174, Tsu-city, Mie 514-8507, Japan. y-kagawa@clin.medic.mie-u.ac.jp
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Kagawa
authors.forename: Takuya
authors.initials: T
authors.lastname: Iwamoto
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Matsuda
authors.forename: Rika
authors.initials: R
authors.lastname: Mukohara
authors.forename: Jun-ichi
authors.initials: J
authors.lastname: Sawada
authors.forename: Michio
authors.initials: M
authors.lastname: Kojima
mesh_terms: D000704:Analysis of Variance; D000889:Anti-Arrhythmia Agents / Q000097:blood / Q000627:therapeutic use; D002191:Canrenoic Acid / Q000097:blood / Q000627:therapeutic use; D004077:Digoxin / Q000097:blood / Q000627:therapeutic use; D016231:Fluorescence Polarization Immunoassay / Q000379:methods*; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D015203:Reproducibility of Results
chemical_list: D000889:Anti-Arrhythmia Agents; D004077:Digoxin; D002191:Canrenoic Acid