Automated homogeneous immunoassay for gentamicin on the dimension clinical chemistry system

Abstract

Background: Monitoring of the concentration of gentamicin in serum and plasma during therapy is widely recommended and practiced in hospitals. Our aim was to develop a homogeneous immunoassay based on particle-enhanced turbidimetric inhibition immunoassay technology to quantify gentamicin on the Dimension® clinical chemistry system. Methods: Assay performance was assessed on each of the Dimension models in a 15-instrument interlaboratory comparison study. A split-sample comparison (n = 1171) was also performed between the gentamicin methods on the Dimension system and the Abbott® TDx® analyzer, using multiple reagent and calibrator lots on multiple instruments. Results: The Dimension method was linear to 25.1 μmol/L (12.0 μg/mL) with a detection limit of 0.63 μmol/L (0.3 μg/mL). Calibration was stable for 30 days. The within-run imprecision (CV) was <1.3%, and total imprecision ranged from 1.8% to 3.2% between 4.2 μmol/L (2.0 μg/mL) and 16.7 μmol/L (8.0 μg/mL) gentamicin. Linear regression analysis of the results on the Dimension method (DM) vs the Abbott TDx yielded the following equation: DM = 0.98TDx - 0.42; r = 0.987. Minimal interference was observed from structurally related compounds such as sagamicin, netilmicin, and sisomicin. Conclusion: The monoclonal antibody used in this method has similar reactivities toward the individual gentamicin subspecies C1, C1a, and C2, thus providing analytical recovery not significantly dependent on relative subspecies concentrations.