Cyclosporin monitoring in Australasia: Survey of laboratory practices in 2000

Abstract

Therapeutic drug monitoring of cyclosporin has been established as part of the routine clinical management of patients following organ transplantation for some 20 years. The current practices of laboratories in Australia and New Zealand have been surveyed for the year 2000 to update previous similar surveys in the light of considerable changes in CsA formulation (now exclusively Neoral throughout Australasia), assay methods, and blood sampling strategies. The results, representing 93% of CsA laboratories in Australasia (n = 44), found that there was still a plethora of approaches adopted within each organ type for monitoring the established trough (C0) CsA concentration. There was a considerable uptake of 2-hour post-dose sampling (C2) monitoring practices, as demonstrated by assay requests to the responding laboratories, particularly in renal and liver transplantation (46% of centers). Most of these laboratories were also assaying C0 and/or to a much lesser extent, so-called limited sampling strategy AUC (lssAUC) samples at this time. The mFPIA (on TDx and AxSYM analyzers) were still strongly represented (54%) (relatively consistent with international data from the UKQAS proficiency testing scheme at this time) despite on-going concerns expressed in the literature about these methods. However, the Cedia assays had made considerable impact so soon after their introduction with 22% of the laboratories using Cedia or Cedia Plus (Microgenics or Roche Diagnostics; Sydney, Australia) methods. There were a wide variety of dilution protocols adopted in many centers for measuring samples above calibration ranges (such as C2 samples), and hence there was scope for improvement to fully validated techniques. Few centers (16%) made any attempt at interpretation of their results, many seeing their role as purely "measuring" (i.e., an analytical role), not "monitoring" (i.e., including assay and result interpretation). Despite many detailed attempts at providing international or national guidelines for CsA monitoring, etc., there is still considerable scope for improving the quality of the laboratory services offered in this complex as well as expensive area. Several respondents volunteered their support for further Australasian CsA monitoring consensus guidelines.