Analytical performance of EMIT cyclosporine assay evaluated

We evaluated the EMIT Cyclosporine Assay (Syva Co., Palo Alto, CA), using the Cobas-Mira analyzer to assess the precision, accuracy, and analytical recovery from whole-blood samples supplemented with cyclosporine. We also performed comparative analysis of whole-blood samples containing cyclosporine from liver and kidney transplant patients by using EMIT, HPLC, and RIA (IncStar Cyclo-Trac, SP assay). Before assay by EMIT or RIA, cyclosporine was extracted from whole blood with methanol. For the HPLC method, whole blood containing cyclosporine was hemolyzed with 300 mL/L acetonitrile in water; cyclosporine was extracted from the hemolysate with acetonitrile. The within-run and between-run CVs for the EMIT assay of cyclospoprine were 9.9% (means = 72.6, SD = 7.2 micrograms/L; n = 20) and 13.5% (means = 75.0, SD = 10.1 micrograms/L; n = 26) for the low control; 3.5% (means = 194.7, SD = 6.8 micrograms/L; n = 20) and 8.1% (means = 189.0, SD = 15.3 micrograms/L; n = 26) for the medium control; and 7.0% (means = 332.5, SD = 23.3 micrograms/L; n = 20) and 7.1% (means = 340.0, SD = 24.2 micrograms/L; n = 24) for the high control (Bio-Rad, whole-blood controls). Analytical recovery of cyclosporine from drug-supplemented samples averaged 99% for EMIT, 104% for HPLC, and 90% for RIA over a concentration range of 50-500 micrograms/L. Analysis of 196 specimens by HPLC (x) vs EMIT (y) gave the following regression statistics: y = 1.27x + 16.44; IncStar's RIA (x') vs EMIT: y = 1.12x' - 2.50; HPLC vs RIA: x' = 1.10x + 23.87.