DETERMINATION OF DIGOXIN IN SERUM - COMPARISON OF RADIOIMMUNOASSAY AND A HETEROGENEOUS ENZYME IMMUNOASSAY

  • 1 January 1978
    • journal article
    • research article
    • Vol. 16  (6) , 335-342
Abstract
The evaluation of a heterogeneous enzyme immunoassay (EIA, subtype ELISA) for the determination of digoxin in [human] serum is described. Results are compared with those obtained from a radioimmunoassay (125I-digoxin). The limit of detection is 0.3 .mu.g/l (0.4 nmol/l). The range of the test is from 0.3-5.0 .mu.g/l (0.4-6.4 nmol/l). Within-batch precision ranged from 7-11%, between-batch precision from 8-14%. Pure digoxin, added to solutions of albumin and pooled sera, gave recoveries between 87-106%. Sera (116) from patients taking digoxin exclusively yielded no systematic difference compared to the results of a radioimmunoassay (RIA) (equation of the bivariate regression: CELISA = 0.954 .cntdot. CRIA + 0.14 (.mu.g/l) (0.18 nmol/l). Marked differences between both tests were observed in individual cases. Digitoxin yielded in vitro and in vivo a cross-reactivity of 7-14% depending on the concentration. In 68 sera from patients, taking digoxin plus spironolactone, results were on the average 0.48 .mu.g/l (0.64 nmol/l) higher with ELISA than with RIA (P < 0.01%). With respect to practicability the ELISA test for digoxin is very similar to the analogous RIA both using the solid phase technique.

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