REDUCING THE COST OF CYCLOSPORINE ASSAYS - MODIFICATION OF THE EMIT-2000 METHOD

Cyclosporin is the leading immunosuppressant agent in organ transplant ation, and therapeutic drug monitoring forms an integral parr of patie nt management in most institutions. In the authors laboratory, the cos t of cyclosporin assays represents a major fraction of total consumabl e expenditure. At present, an average of 4,300 patient cyclosporin ass ays are performed annually using the EMIT 2000 method (Behring-Syva) o n the Cobas Mira analyser (Roche), at a cost of AUD$50,000 in kits alo ne. As a means of reducing laboratory costs, the manufacturer's recomm ended method was modified by decreasing all of the reagent and sample volumes in the ''Analytical'' section of the Cobas Mira cyclosporin pr ogramme by 33%. Assay performance was monitored over a 10-month period and compared to that of the unmodified method. Calibration curves wer e stable, requiring a one-point correction on average of once every 12 days, and a full calibration once every 1.7 months. Interassay variab ility was not different to that previously reported for the unchanged method, with mean (SD, CV) concentrations for trilevel quality control specimens of 86.5 mu g/L (10.2, 11.9%), 185.9 mu g/L (11.4, 6.2%) and 408.5 mu g/l (28.9, 7.1%). From 24 specimens assayed in an internatio nal quality assurance programme, the results of 23 were within 1.2 SD of the group mean for the EMIT method, with an average bias of 0.8%. W ith the current modifications, we were able to perform an average of 1 05 patient assays per kit compared to the previous 71, equating to an annual saving of AUD$16,600.