Cloned enzyme donor immunoassay tacrolimus assay compared with high-performance liquid chromatography-tandem mass spectrometry and microparticle enzyme immunoassay in liver and renal transplant recipients.

The immunosuppressant drug tacrolimus has a narrow therapeutic index and is subject to a large variation in individual bioavailability and clearance. With its narrow therapeutic index, therapeutic drug monitoring is standard clinical practice in the management of transplant recipients. In this study, we report the evaluation of the cloned enzyme donor immunoassay (CEDIA) for the determination of whole-blood tacrolimus concentrations compared with high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) and microparticle enzyme immunoassay (MEIA) using samples obtained from liver (n = 100) and renal (n = 88) transplant recipients. Linear regression analysis showed a relationship of CEDIA = 1.24 HPLC-MS/MS -0.18 (r = 0.81). The mean bias (+/-SEM) for all patients when compared with HPLC-MS/MS was 22.2% (+/-2.1%). The precision of the CEDIA method for all samples showed a root mean square error of 3.1 microg/L. Liver transplant recipient samples showed a mean (+/-SEM) bias compared with HPLC-MS/MS of 12.5% (+/-1.6%). The precision of the CEDIA method for these samples showed a root mean square error of 1.5 microg/L. The data suggest that in the renal transplant group, the CEDIA and MEIA methods have a bias of 33.3% and 20.1%, respectively, compared with HPLC-MS/MS. The CEDIA tacrolimus immunoassay has been shown to be a rapid method for the determination of whole-blood tacrolimus concentrations and may be considered when HPLC-MS/MS is not available. When used in the clinical setting with other parameters, it would be a useful adjunct in the management of liver transplant recipients, but a significant bias in renal transplant patients needs to be further investigated.