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5th International Conference on New Trends in Clinical and Experimental Immunosuppression

EVALUATION OF THE NEW EMIT ENZYME IMMUNOASSAY FOR THE DETERMINATION OF WHOLE BLOOD TACROLIMUS CONCENTRATIONS IN KIDNEY, HEART AND LIVER-TRANSPLANT RECIPIENTS
Cees J. Hesse Carla C. Baan Aggie H.M.M. Balk Herold J. Metselaar Willem Weimar Teun van Gelder
Internal Medicine, Erasmus Medical Center, Rotterdam, The Netherlands; Cardiology, Erasmus Medical Center, Rotterdam, The Netherlands

Objectives: Tacrolimus is a potent immunosuppressant drug used in the field of organ transplantation. Due to its narrow therapeutic window frequent drug monitoring is recommended. Most commercially available methods for routine monitoring have been immunoassay based, utilizing an anti-tacrolimus monoclonal antibody. In this study the faster EMIT 2000 Tacrolimus Immunoassay (Dade-Behring) was compared with the currently most used microparticle immunoassay (MEIA II, Abbott). Methods: Both methods were performed according to the manufacturer's instructions with slight modifications in the extraction procedures in both methods. Qualitycontrol samples at 5, 11 and 22 µg/L were run in each assay to ensure assay integrity in both methods. Multiple trough samples from kidney (144 samples from 69 patients), heart (49 samples from 32 patients) and liver transplant recipients (49 samples from 28 patients) were analyzed. Results: The inter-assay imprecision (%CV) of the quality-control samples (n=18) were respectively 11.7, 5.6 and 4.6% with the EMIT method and 14.7, 7.4 and 7.9% with the MEIA method. PassingBablok regression analysis yielded the following line of best fit equations EMIT= 0.982 (range 0.937 to 1.023)x MEIA + 0.12 (-0.19 to 0.46) µg/L (95% confidence interval, n=233). The organtransplant subgroups heart, kidney and liver also showed comparable results by both methods. Bland-Altman plots of the difference in both methods against the average concentration of both methods showed no differences between both methods. The 95% confidence interval of the differences in the BlandAltman plot was 3.04 µg/L and was constant over the whole range. Conclusions: The EMIT method is a good alternative for the currently most used MEIA method in the therapeutic monitoring of tacrolimus in kidney-, heart- and liver-transplant recipients. The %CV of the EMIT method is slightly better, there is no need for frequent recalibration and the use of a random-access analyser allows a quick analysis of a few samples with a low turnaround time and as well no limits to the number of samples analyzed during a run.