Comparative evaluation of three methods for measuring gentamicin and tobramycin in serum.

Three procedures (radioimmunoassay, fluorescence immunoassay, and enzyme immunoassay) for the determination of gentamicin and tobramycin levels were compared. These systems were evaluated on the basis of accuracy, reproducibility, specificity, and cost. All three systems showed a high degree of accuracy and precision. The fluorescence immunoassay gave significantly lower values for gentamicin and tobramycin at levels below 5 microgram/ml. Of the three systems, the radioimmunoassay was the least expensive, provided that a minimum of 10 analyses were performed daily; single tests required more technical time and were more costly. Costs of single tests by fluorescence immunoassay and enzyme immunoassay systems were similar. The enzyme immunoassay system performed equally well for both gentamicin and tobramycin in giving rapid and accurate results.