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.