Evaluation of EMIT Adapted to the (Cobas) Bio Centrifugal Analyzer

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Abstract
EMIT [enzyme multiplied immunoassay technique] assays for the determination of phenytoin, methotrexate, disopyramide, digoxin and thyroxine were adapted to the Cobas Bio centrifugal analyzer and compared with the corresponding laboratory routine procedures. Evaluation of the data from the Cobas Bio by 5 different mathematical models showed that the 4-parameter logit model correlated best with the comparison procedures and the originally recommended calculation model for the reagent lots used in the study. The precision of the EMIT phenytoin, methotrexate and disopyramide assays was in most cases very good (between-days coefficients of variation 1.6-7.5%). A lower precision was observed with the EMIT digoxin assay (between-days coefficient of variation 9.2-16.8%) and at low concentrations also with the EMIT thyroxine assay (3.1-21.4%). Calibration curves of the EMIT phenytoin and methotrexate assays were stable for at least 1 h. The results from the determination of phenytoin, methotrexate and disopyramide in patient samples by use of the Cobas Bio were in good agreement with those values obtained with the EMIT/LAB. The data determined with the EMIT digoxin assay adapted to the Cobas Bio correlated better with those of a radioimmunoassay than the values measured with the EMIT/LAB system. The results of thyroxine determinations with EMIT by use of the Cobas Bio and the original procedure with an ABA-100 were in good agreement and on average .apprx. 12% lower than those measured by radioimmunoassay. The Cobas Bio allows rapid determinations with EMIT and a reduction in direct costs of up to 85%.