Automated homogeneous immunoassay for gentamicin on the dimension clinicalchemistry system

Background: Monitoring of the concentration of gentamicin in serum and plas ma during therapy is widely recommended and practiced in hospitals. Our aim was to develop a homogeneous immunoassay based on particle-enhanced turbid imetric inhibition immunoassay technology to quantify gentamicin on the Dim ension(R) 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 Dimens ion system and the Abbott(R) TDx(R) analyzer, using multiple reagent and ca librator lots on multiple instruments. Results: The Dimension method was linear to 25.1 mu mol/L (12.0 mu g/mL) wi th a detection limit of 0.63 mu mol/L (0.3 mu g/mL). Calibration was stable for 30 days, The within-run imprecision (CV) was <1.3%, and total imprecis ion ranged from 1.8% to 3.2% between 4.2 mu mol/L (2.0 mu g/mL) and 16.7 mu mol/L (8.0 mu g/mL) gentamicin. Linear regression analysis of the results on the Dimension method (DM) vs the Abbott TDx yielded the following equati on: 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 reactiv ities toward the individual gentamicin subspecies C1, C1a, and C5 thus prov iding analytical recovery not significantly dependent on relative subspecie s concentrations. (C) 1999 American Association for Clinical Chemistry.