Comparison of digoxin analysis by EMIT with Immophase and Dac-Cel radioimmunoassay

The results obtained by an enzyme multiplied immunoassay kit, EMIT, for the measurement of serum digoxin concentration were compared with those from two radioimmunoassay kit methods, Immophase and Dac-Cel. Patients' sera were used to study the correlation between the methods, and three quality control sera with low, intermediate, and high digoxin concentrations were used to study individual method precision. The coefficients of correlation between the three methods varied between 0.915 and 0.951 for serum drug concentrations up to 4.5 nmol/l. There were statistically significant differences between the means of the patients' samples for each method. Precision was acceptable for each method: within-batch percentage coefficient of variation (%CV) less than 8, between-batch %CV less than 10, except for Dac-Cel at low concentration %CV = 18.6. The time taken for the analysis of a batch of 10 samples was between 1.5 and 2 hours, depending on the method.