A COMPARISON OF THE OPUS AND TDX ANALYZERS FOR ANTIEPILEPTIC DRUG-MONITORING

Therapeutic drug monitoring of a variety of antiepileptic drugs is use d routinely as a guide to individualising the drug treatment of patien ts with epilepsy. Thin dry film multilayer immunoassays (OPUS) for car bamazepine, phenytoin, phenobarbitone, and valproic acid were evaluate d and compared with fluorescence polarisation immunoassay (TDx), using commercially available control material and patient sera. For the OPU S, the within-batch coefficient of variation (CV) for the different dr ugs in the control material varied between 3.9% (phenobarbitone) and 8 .1% (valproic acid). The between-batch CVs varied between 5.3% (valpro ic acid) and 18.3% (carbamazepine). The comparative between-batch CVs for the TDx varied between 2.0% (phenytoin) and 7.0% (valproic acid). Analysis of 209 patient samples containing carbamazepine, phenytoin, p henobarbitone, or valproic acid demonstrated significant correlation b etween the two analytical methods, with correlation coefficients of 0. 9336, 0.9560, 0.9448, and 0.9618, with slopes of the regression lines of 0.9042, 0.8663, 1.1368, and 1.1244, respectively. It is concluded t hat both the TDx and OPUS instruments exhibit comparable performance f or the analysis of carbamazepine, phenobarbitone, phenytoin, and valpr oic acid in patient samples. Moreover, the OPUS instrument, with its f acilities of random assay access and statim analysis, may be useful in an outpatient setting in which a major consideration would be a rapid turnaround of patient assay results.