Particle concentration fluorescence immunoassay of gentamicin

We report the development of a particle concentration fluorescence immunoassay (PCFIA) for gentamicin using commercially available reagents. The solid phase consists of 0.8 microns polystyrene spheres to which gentamicin antibody is noncovalently bound. Fluorescein-labeled gentamicin serves as the tracer. The assay is carried out on 96-well reaction plates and read using an automated instrument. The assay is accurate over the range of gentamicin concentrations commonly encountered in clinical practice, with day-to-day coefficients of variation of 3-7%. As little as 0.01 mg/L of gentamicin can be detected when sample predilution is omitted. PCFIA is compared with Abbott TDX fluorescence polarization immunoassay for the measurement of serum gentamicin concentrations in routine clinical specimens.