A comparison of the homogeneous enzyme immunoassay and polarization fluoroimmunoassay of gentamicin.

Polarization fluoroimmunoassay (Abbott TDX) and the homogeneous enzyme immunoassay (Syva, EMIT) both allowed the rapid, accurate and precise assay of gentamicin. The presence of other antibiotics, Intralipid and gentamicin from various sources on the assay was assessed. The results obtained for both methods correlated well with the plate microbiological method (TDX correlation coefficients, spiked samples 0.98, patient samples 0.95; EMIT correlation coefficients, spiked samples 0.99, patient samples 0.94). The coefficients of variation (CV) for within assay studies were between 3.5 and 5.9% and between 5.5 and 6.2% for the TDX and EMIT procedures respectively. The CVs for the between assay studies were between 2.4 and 5.9% and from 3.2 and 14.8% for TDX and EMIT respectively. The presence of 'Intralipid' affected the two assays to differing extents but other antimicrobial agents did not. Attention is drawn to the fact that results may be influenced by standard gentamicin material obtained from different sources.