Monitoring cyclosporin A (ciclosporin, INN) concentrations in whole blood: evaluation of the EMIT assay in comparison with HPLC and RIA.

We report here on an evaluation of the enzyme-multiplied immunoassay technique (EMIT) from Syva for cyclosporin A (ciclosporin, INN) concentration measurements in whole blood. The assay incorporates a monoclonal 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 selective radioimmunoassay (INCStar). Ciclosporin concentrations determined by EMIT (y) agreed very well with those by RIA, and averaged 8% higher than those by HPLC (x) [n = 197, mean = 143 micrograms/l, y = 155 micrograms/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 micrograms/l, and from 5.5% to 10.5% for ciclosporin concentrations between 69.5 micrograms/l and 100 micrograms/l. The within-series CV for a concentration of 45.5 micrograms/l was 14.8%. Calibration employing a 2-point mode instead of a continuous mode of UV-signal evaluation improved the precision of the EMIT assay at low ciclosporin concentrations. Sample pretreatment required thorough and skillful performance to avoid false positive ciclosporin measurements. We conclude that the EMIT assay is specific, and rapid to perform. It can be effectively used in the monitoring of ciclosporin concentrations in whole blood.