STUDY OF THE CORRELATION BETWEEN MEIA AND ELISA METHODS FOR FK-506 DETERMINATION IN LIVER-TRANSPLANT RECIPIENTS

Background and objectives: FK 506 is an immunosuppressive macrolide ad vocated for prevention of graft rejection. Plasma or blood FK 506 leve ls must be determined to strike a balance between FK 506 toxicity and graft rejection. The first aim of this study was to compare an automat ed microparticle enzyme immunosorbent assay (MEIA) method (on whole bl ood) with the reference enzyme-linked immunosorbent assay (ELISA) meth od (on plasma). A second aim was to compare the two methods for predic tion of FK 506 nephrotoxicity. Patients and methods: Forty-seven patie nts were studied comprising 128 samples. All were treated with FK 506 on a compassionate basis. For each patient, the concentrations of FK 5 06 were determined in plasma by means of ELISA and in whole blood by M EIA. Results: The repeatability and the reproducibility of these two m ethods were similar. The interpatient correlation coefficient between MEIA and ELISA, determined on 128 samples from 47 liver recipients, wa s satisfactory (r = 0.82). From these 47 patients, the intra-patient c orrelation coefficients were calculated for 17 of them. The intrapatie nt correlation coefficients were between 0.63 and 0.98 for 15 patients , and between 0.26 and 0.55 in the remaining two cases. Mean creatinin e plasma levels in the 55 samples below the median FK 506 value in the MEIA method and in the 55 with values above the median (120 and 134 m u mol/litre, respectively) were significantly different (P < 0.05), as were those using the reference ELISA methods (115 and 139 mu mol/litr e, P < 0.01). In contrast, there was no significant difference between the mean creatinine plasma levels in the 55 samples with FK 506 level s below the median using both methods or between those above the media n. Conclusion: The automated MEIA method, being simpler and more rapid than the ELISA method, should now be preferred for therapeutic monito ring of FK 506.