Correlation of bioluminescent assay of gentamicin in serum with agar diffusion assay, latex agglutination inhibition card test, enzyme immunoassay, and fluorescence immunoassay.

An improved bioluminescent assay of gentamicin in serum, based on the dose-dependent effect of the agent on the accumulation of extracellular ATP in Escherichia coli LU 14 cultures, is presented. The accuracy of the bioluminescent assay of gentamicin, expressed as the mean coefficient of variation over the therapeutic range, was 2.8%. Corresponding figures for an agar diffusion assay, a latex agglutination inhibition card test, an enzyme immunoassay, and a fluorescence immunoassay were 6.4, 17.5, 4.2, and 9.4%, respectively. All of the methods correlated well (r = 0.926 to 0.976), with the possible exception of the card test (r = 0.777 to 0.841). The bioluminescent assay requires only 1 microliter of serum, which allows for capillary sampling, and results are available within 75 min.