Evaluation of five immunological methods for the assay of serum netilmicin

Three specific immunological methods for the determination of netilmicin and two enzyme immunoassays for gentamicin were compared for assaying serum netilmicin. The commercial kits we used were Radioimmunoassay (RIA), Substrate Labelled Fluorescence Immunoassay (gentamicin) ( SLFIA ), Homogeneous Enzyme Immunoassay (gentamicin and netilmicin) (EMIT) and Fluorescence Polarization Immunoassay ( FPIA ). After analysing spiked calf serum samples in the range of 0-15.8 mg X 1(-1) netilmicin, extensive statistical analysis was performed. The Performance Index was used to qualify the different methods. Results show that the SLFIA (gentamicin) kit is a very acceptable method for the determination of serum netilmicin levels, well comparable with the EMIT (gentamicin) kit and the EMIT (netilmicin) kit. FPIA and RIA require expensive specialized apparatus so it is only economically feasible when other drugs or substances are also determined on the same apparatus. The abilities and specific needs of each laboratory will play an important role in the choice of a method, because the tested kits are all within the range we need from a clinical point of view.