Assay of gentamicin in serum: a comparison of four methods

The performance of radioimmunoassay (RIA), fluoroimmunoassay (FIA) and enzyme immunoassay (Emit) in the analysis of serum gentamicin concentrations in 62 patient samples was compared with the standard bioassay (agar plate growth inhibition method). All methods gave satisfactory reproducibility in the concentration range of 1-12 microgram/ml. Coefficient of variation was the smallest with Emit. In all cases there was a statistically significant correlation between the results gained by the four methods. RIA, FIA, and Emit seem to give somewhat higher levels than bioassay in the low concentrations. The opposite was true at high concentrations. The new methods are much faster than bioassay but need special instrumentation. The choice of the method depends mainly on the local conditions and needs.