Switching from HPLC/UV to MEIA for whole blood sirolimus quantitation: comparison of methods

Abstract

Sirolimus is a immunosuppressive agent for renal transplant recipients. Monitoring of whole blood sirolimus concentration is necessary in order to improve clinical outcomes. An increasing number of clinical laboratories (4-14% during 2005) are using microparticle enzyme immunoassay (MEIA) for sirolimus quantitation but previous reports indicated a high variability, with a mean difference of 17% for MEIA method vs. high-performance liquid chromatography/ultraviolet (HPLC/UV). This study was aimed at comparing the reliability of MEIA with the HPLC/UV method. Blood samples from transplant patients were processed using both HPLC/UV and MEIA assays. Comparison and Bland-Altman plots, as well as regression analysis and paired t-test were used to compare results of the assays. Concentrations were stratified into three groups and used to investigate whether any observed difference between methods could be influenced by sirolimus concentration. Regression analysis yielded a coefficient of correlation R of 0.9756, the line of best fit being y=0.9832x+0.1976. The statistical analysis showed no difference between the two sets of experimental data. The average percentage difference between the two methods was found to be -0.2+/-19.2%. On the basis of our present results, the tested MEIA assay is able to quantify sirolimus concentration with a clinically acceptable imprecision, similar to that of HPLC/UV method.

Determination of blood sirolimus concentrations in liver and kidney transplant recipients using the Innofluor® fluorescence polarization immunoassay: Comparison with the microparticle enzyme immunoassay and high-performance liquid chromatography-ultraviolet method

“…Although some authors have found similar results using MEIA and HPLC ( 7 , 8 , 10 , 12 ), it is generally accepted that the MEIA leads to an overestimation of the sirolimus concentration in patients’ samples, related to the antibody reacting with hydroxyl- and desmethyl-sirolimus metabolites ( 4 – 6 , 9 , 11 , 13 , 25 ). The FPIA and MEIA assays provided similar results, with a high correlation coefficient between them, and a standard error of the estimate only slightly higher than the acceptable value ( Figure 1 E).…”