EVALUATION OF EMIT(R) CYCLOSPORINE ASSAY FOR USE WITH WHOLE-BLOOD

We evaluated the EMIT(R) Cyclosporine Assay, designed for specific qua ntification of cyclosporine (CsA) in whole blood. The assay was run on the Roche Cobas Mira(TM) or Cobas Mira S(TM) analyzer. Analytical rec overy from both normal donor whole blood and transplant patients' samp les was within 17% of the standards. Measurement of diluted out-of-ran ge samples also yielded excellent recovery (101-105%). Within-run, bet ween-run, and total CVs were less-than-or-equal-to 8.1%, 10.9%, and 12 .1%, respectively. The detection limit was <32 mug/L. The assay was li near from 0 to 500 mug/L. No significant cross-reactivity was observed for CsA metabolites AM1, AM19, and AM4N. Slight cross-reactivity occu rred with metabolite AM9; 670 mug/L AM9 increased the measured CsA con centration by 49 mug/L. High concentrations of bilirubin, uric acid, t riglycerides, and cholesterol, as well as 54 commonly coadministered d rugs did not interfere with CsA quantification. Similarly, neither ext reme values of hematocrit nor choice of anti-coagulant affected CsA re covery. Sample extract stability was >4 h, and assay calibration was s table for at least 2 weeks. Patients' samples analyzed by the EMIT ass ay showed strong correlation with both HPLC and I-125-RIA (r>0.97). We conclude that the EMIT Cyclosporine Assay provides a convenient, accu rate, and precise method for specific quantification of CsA in whole b lood.