MONITORING CYCLOSPORINE-A (CYCLOSPORINE, INN) CONCENTRATIONS IN WHOLE-BLOOD - EVALUATION OF THE EMIT(TM) ASSAY IN COMPARISON WITH HPLC AND RIA

We report here on an evaluation of the enzyme-multiplied immunoassay t echnique (EMIT(TM)) from Syva for cyclosporin A (ciclosporin, INN) con centration measurements in whole blood. The assay incorporates a monoc lonal antibody for specific determination of ciclosporin. Measurements by EMIT were performed on the Cobas Mira-S from Roche. A total of 197 blood specimens from heart- (n = 74), kidney- (n = 62) and liver- (n = 61) transplant recipients were analyzed. EMIT values correlated well with those obtained by HPLC, as well as with those obtained by a sele ctive radioimmunoassay (INCStar). Ciclosporin concentrations determine d by EMIT (y) agreed very well with those by RIA, and averaged 8% high er than those by HPLC (x) [n = 197, xBAR = 143 mug/l, yBAR = 155 mug/l , y = 1.09x-0.6, r = 0.969]. Within-series and between-days CVs ranged from 4.6% to 7.3% for ciclosporin concentrations > 100 mug/l, and fro m 5.5% to 10.5% for ciclosporin concentrations between 69.5 mug/l and 100 mug/l. The within-series CV for a concentration of 45.5 mug/l was 14.8%. Calibration employing a 2-point mode instead of a continuous mo de of UV-signal evaluation improved the precision of the EMIT assay at low ciclosporin concentrations. Sample pretreatment required thorough and skilful performance to avoid false positive ciclosporin measureme nts. We conclude that the EMIT assay is specific, and rapid to perform . It can be effectively used in the monitoring of ciclosporin concentr ations in whole blood.