EVALUATION OF 5 IMMUNOASSAYS FOR THE DETERMINATION OF DIGOXIN IN SERUM

Five immunoassays for the determination of digoxin have been evaluated (Digoxin II, Abbott; Cedia Digoxin XL, Microgenics; Coat-a-Count Digo xin, Diagnostic Procedure Corporation, DPC; ''On-line'' Digoxin, Roche Diagnostic Systems; EMIT 2000 Digoxin, Syva). Four of them required n o sample pre-treatment. The methods included a radioimmunoassay, fluor oimmunoassay, two enzyme-immunoassays and a turbidimetric immunoassay; the last three mentioned were adapted to the Cobas(R) Mira Plus. The intra- and inter-assay precision was lower than 9%, except for Microge nics. The calibration stability fluctuated from 120 days for Abbott to 27 days for the Poche test, 7 days for the Syva assay and 2 days for Microgenics. The DPC test was not assayed for calibration stability. T he interference from ''digoxin-like immunoreactive factor(s)'' differe d according to the assay. The highest interference was seen with Abbot t and Microgenics, and the lowest with the DPC test. The comparison am ong all the methods offered values of ''r'' higher than 0.95 except be tween Microgenics and Syva assays where ''r'' was 0.896. The results o btained with Poche and Microgenics were higher than 12% of the remaini ng assays.