Comparative evaluation of the Abbott TDX, the Abbott ABA200, and the Syva LAB5000 for assay of serum gentamicin.

Three automated chemical assays for serum gentamicin were compared for accuracy, reproducibility and cost. One method utilized fluorescence polarization (Abbott TDX), and the other two enzyme-multiplied immunoassay (Abbott ABA200, and the Syva Lab5000). All three systems produced a high degree of accuracy and reproducibility with spiked samples when the concentrations of gentamicin were within the range of 3.0-8.0 mg/l. However, with concentrations below 2.0 mg/l or above 8.0 mg/l, only the TDX system gave acceptable coefficients of variation and accurate recoveries. Similarly, excellent correlations were obtained between all three systems for assays of clinical specimens containing 2.0-8.0 mg/l gentamicin, but above and below this range, the correlations were poor except between TDX and Lab5000 within the range of 0.0-2.0 mg/l. The Abbott TDX was thus the most accurate and reproducible of the three systems for the assay of serum gentamicin in the critical concentrations below 2.0 mg/l and above 8.0 mg/l. The cost per assay by the Abbott TDX was US$4.57 compared with US$5.40 for the Abbott ABA200, and US$3.20 for the Syva Lab5000.