Comparison of ELISA method versus MEIA method for daily practice in the therapeutic monitoring of tacrolimus

Background. For the adequate management of transplant patients on tacrolimus therapy, it is important to obtain optimal blood concentrations. The purpose of this study was to determine the most appropriate method for daily practice of tacrolimus determination in whole blood. We compared enzyme-linked immunosorbent assay (ELISA) with microparticle enzyme immunoassay (MEIA), using European controls and blood samples from organ graft recipients treated with tacrolimus. Time, practicability and cost were considered also. Methods. The assays were performed according to the procedures detailed in the product inserts. In five European controls and 40 blood samples from kidney and liver transplant patients, we determined the blood levels of tacrolimus by both MEIA and ELISA tests. Results. MEIA gave more reliable results with the European controls (y = 1.078x + 0.092; r = 0.996) than ELISA (y = 0.956x + 1.307; r = 0.946). For the patient samples, the correlation between the two tests was 0.85 and the extreme range of values was + 65% and -56% for ELISA vs MEIA. Although the manufacturer of the ELISA test used claims the best sensitivity and precision, in our experience the MEIA test was quicker and cheaper. Conclusions. MEIA provides a quick, reliable and easy-to-handle method for routine monitoring of tacrolimus blood levels.