In this study we used the Opus Diagnostic system to determine drug concentrations in undiluted serum or plasma. The assay is based on the dry multilayer film technology for low molecular weight analytes such as therapeutic drugs. The polysaccharide layers are coated onto a plastic base. The signal layer contains an immobilized antibody and a fluorescent-labeled hapten. For high molecular weight analytes (digoxin) a fluorogenic ELISA is provided in self-contained test modules. Analytical imprecision studies were performed at low, medium and high concentrations. For intra-day assays, valproic acid, phenobarbital and theophylline showed a CV less than 10% at all the levels tested. Phenytoin showed a CV less than 10% at low and middle levels. For carbamazepine the CV was less than 10% at middle and high levels. For digoxin the CV was less than 10% only at high levels. The inter-day variability showed at low levels, a CV less than 10% for valproic acid and phenobarbital; for the other drugs tested it was more than 10%. At medium and high levels, it was less than 10% for all the drugs. The linearity check, performed for carbamazepine, phenobarbital, phenytoin and theophilline, was acceptable. Calibration stability studies demonstrated that the curves were stable for seven weeks except for the digoxin curve which became evidently unstable after two weeks. Comparison with fluorescent polarization immunoassay (Abbott TDX) showed the following correlations: valproic acid r = 0.94, slope(s) = 0.92, intercept(i) = 0.59; carbamazepine r = 0.94, s = 0.89, i = 0.12; digoxin r = 0.74, s = 0.61, i = 0.21; phenobarbital r = 0.97, s = 0.96, i = -0.97; phenytoin r = 0.95, s = 0.81, i = 0.46, theophylline r = 0.95, s = 0.74, i = 0.60. These data show that, in the same samples, the Opus concentrations values were always lower than those of TDX: from 3.5% for valproic acid to 26% for theophylline. These underestimations could be due to the different kind of antibodies used (monoclonal and respectively polyclonal) and to the different methodologies used. As they are constant, for a clinical utilisation, the therapeutic ranges should be established accordingly.
|Translated title of the contribution||Evaluation of OPUS analyse in drugs monitoring|
|Number of pages||8|
|Journal||Giornale Italiano di Chimica Clinica|
|Publication status||Published - 1993|
ASJC Scopus subject areas
- Clinical Biochemistry