Comparison of the Reintroduced MEIA® Assay With HPLC-MS/MS for the Determination of Whole-Blood Sirolimus From Transplant Recipients

Abstract

Therapeutic monitoring with dosage individualization of sirolimus drug therapy is standard clinical practice for organ transplant recipients. For several years sirolimus monitoring has been restricted as a result of lack of an immunoassay. The recent reintroduction of the microparticle enzyme immunoassay (MEIA) for sirolimus on the IMx analyser has the potential to address this situation. This study, using patient samples, has compared the MEIA sirolimus method with an established HPLC-tandem mass spectrometry method (HPLC-MS/MS). An established HPLC-UV assay was used for independent cross-validation. For quality control materials (5, 11, 22 microg/L), the MEIA showed acceptable validation criteria based on intra- and inter-run precision (CV) and accuracy (bias) of <8% and <13%, respectively. The lower limit of quantitation was found to be approximately 3 microg/L. The performance of the immunoassay was compared with HPLC-MS/MS using EDTA whole-blood samples obtained from various types of organ transplant recipients (n = 116). The resultant Deming regression line was: MEIA =1.3 x HPLC-MS/MS + 1.3 (r = 0.967, S(y/x) = 1) with a mean bias of 49.2% +/- 23.1% (range, -2.4% to 128%; P<0.001). The reason for the large and variable bias was not explored in this study, but the sirolimus-metabolite cross-reactivity with the MEIA antibody could be a substantive contributing factor. Whereas the MEIA sirolimus method may be an adjunct to sirolimus dosage individualization in transplant recipients, users must consider the implications of the substantial and variable bias when interpreting results. In selected patients where difficult clinical issues arise, reference to a specific chromatographic method may be required.

Simultaneous LC–MS–MS determination of cyclosporine A, tacrolimus, and sirolimus in whole blood as well as mycophenolic acid in plasma using common pretreatment procedure

“…However, the use of immunoassays is costly and the comparison of results with those obtained by more specific HPLC or liquid chromatography-tandem mass spectrometry (LC-MS-MS) procedures show generally overestimation, caused by limited selectivity of all assays. This was reported for TCR [1,2], MPA [3], SIR [4][5][6][7][8], and CsA [9].…”

Successful and cost-efficient replacement of immunoassays by tandem mass spectrometry for the quantification of immunosuppressants in the clinical laboratory

“…The major advantage of such assays is their ease of operation, and also that they are performed on instrument platforms used for other immunoassays and which are sometimes already installed in the laboratory. However, the major inconvenient of these assays is the lack of specificity for the parent drug vs. drug metabolites or structurally related compounds, as exemplified by the fact that immunoassays tend to overestimate immunosuppressant drug levels when compared to chromatographic methods (see Section 3.3 and [16][17][18][19][22][23][24][25][26]). Since different immunoassays show variable degrees of specificity, assay-specific therapeutic ranges should be established and the long-term therapeutic monitoring of patients should be done using the same method.…”

“…Even though immunoassays for the quantification of immunosuppressant drugs usually require a manual sample pretreatment step (red blood cells lysis, centrifugation, and collection of the supernatant) before analysis on the automatic analyzer, the ease of execution and the rapid turnaround time of these assays still constitute a major advantage. On the other hand, immunoassays are very costly (>$10 per sample) and their specificity varies as antibodies can cross-react with drug metabolites [10,[16][17][18][19].…”

Determination of sirolimus in rabbit arteries using liquid chromatography separation and tandem mass spectrometric detection

“…The concentration of sirolimus in the circulation varies with time after placement. Many means can be used to determine the sirolimus concentration in whole blood (Volosov et al, 2001;Napoli and Taylor, 2001;Streit et al, 2002;Vogeser et al, 2002;Pieri et al, 2005;Morris et al, 2006). However, sirolimus concentrations in the tissue vary significantly with the distance from the stents and with time.…”