title: Comparability of a new turbidimetric digoxin test with other immunochemical tests and with HPLC--a multicenter evaluation.
abstract: A new turbidimetric inhibition immunoassay for digoxin (Tina-quant [a] Digoxin, Boehringer Mannheim) was evaluated in seven laboratories. It can be performed without sample pretreatment with ready-to-use reagents on nondedicated analyzers in combination with routine clinical chemistry. The studies revealed a good analytical performance: lower limit of detection 0.12 microg/L (3 SD from mean of blank); linearity up to 7.5 microg/L; median between-run CVs 8.1% (0.6 microg/L), 2.8% (1.5 microg/L), 1.9% (3 microg/L); mean analytical recovery in control sera 98-102%; slopes from 0.97 to 1.09 and intercepts from -0.28 to 0.10 microg/L in comparison with four immunoassays; and a high resistance to common interferents. The test was more resistant to digoxin-like immunoreactive factor (DLIF) interference than other methods, showing cross-reactivity only in some intensive care patient samples. Among 192 patients in whom DLIF is expected (e.g., pregnant women, patients with renal failure, newborns), 90% of results were < or =0.26 microg/L digoxin. Cortisol showed no cross-reactivity and digoxigenin had a low reactivity. An interlaboratory survey revealed a good comparability of the Tina-quant [a] test with the median of all methods (slope 0.99, intercept -0.06 microg/L). An HPLC method for digoxin based on isocratic separation of samples on an RP-18 column followed by detection by an immunoassay yielded a reasonable comparability with the immunochemical tests with noncritical samples. Divergent results of immunoassays caused by DLIFs or different cross-reactivities with digoxin metabolites or derivatives can be explained by the use of this HPLC method.
authors.affiliation: Klinisch-Chemisches Laboratorium, Kantonsspital Basel, Switzerland. scholer@ubaclu.unibas.ch
authors.forename: A
authors.initials: A
authors.lastname: Scholer
authors.forename: J
authors.initials: J
authors.lastname: Boecker
authors.forename: U
authors.initials: U
authors.lastname: Engelmayer
authors.forename: K
authors.initials: K
authors.lastname: Feldmann
authors.forename: D
authors.initials: D
authors.lastname: Hannak
authors.forename: R
authors.initials: R
authors.lastname: Kattermann
authors.forename: M
authors.initials: M
authors.lastname: Oellerich
authors.forename: H
authors.initials: H
authors.lastname: Raith
authors.forename: H
authors.initials: H
authors.lastname: Schlebusch
authors.forename: H
authors.initials: H
authors.lastname: Wieland
authors.forename: D
authors.initials: D
authors.lastname: Willems
authors.forename: J
authors.initials: J
authors.lastname: Jarausch
authors.forename: I
authors.initials: I
authors.lastname: Domke
mesh_terms: D000925:Anticoagulants; D002851:Chromatography, High Pressure Liquid; D003422:Critical Care; D004077:Digoxin / Q000097:blood*; D005260:Female; D006801:Humans; D007118:Immunoassay / Q000379:methods* / Q000706:statistics & numerical data; D007202:Indicators and Reagents; D007231:Infant, Newborn; D007753:Laboratories; D009391:Nephelometry and Turbidimetry / Q000379:methods*; D011247:Pregnancy; D011786:Quality Control; D012016:Reference Values; D006435:Renal Dialysis; D051437:Renal Insufficiency / Q000097:blood; D012680:Sensitivity and Specificity
chemical_list: D000925:Anticoagulants; D007202:Indicators and Reagents; D004077:Digoxin