Experiences with the enzyme-multiplied immunoassay cyclosporine specific assay in a therapeutic drug monitoring laboratory.

Cyclosporin-A (CsA) monitoring is well established in the management of most organ transplant patients. The present communication reviews the performance of the recently introduced specific enzyme-multiplied immunoassay (EMIT) CsA method during the first 7 months of its operation and compares costs of providing this service with those of the specific 125I radioimmunoassay (RIA) method previously employed in this clinical laboratory. Results suggest that the EMIT method performed well, giving long calibration curve stability (up to 12 weeks), and only 4.4% of the 31 kits through this period were consumed in assaying calibration standards compared with 20.8% with RIA. However, more quality control assays were performed, with the net result that only a slight improvement in the percentage of kit consumed in patient assays was noted (74.0% compared with 70.3%) with the EMIT method. This method appears to have been well accepted clinically as the CsA assay request rate over this period increased by 23% and, since it is both specific and rapid, is, therefore, recommended as the best CsA method currently available.