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Objectives: This study compared the performance of a fluorescent polarization immunoassay (FPIA) against HPLC-tandem mass spectrometry (HPLC-MS) for the measurement of everolimus in renal transplant recipients. Design and methods: A total of 333 pre-dose samples from 45 renal transplant patients were analyzed by FPIA and HPLC-MS. Results: The inter-batch inaccuracy and precision of the FPIA for control samples were ≤6% and ≤13.0%, respectively ( n = 17). The comparison of patient results yielded the Deming regression equation FPIA = 1.19 × HPLC-MS + 0.51. The mean bias was 24.4% (95% CI: −3.0 to 54.2%, range: −30.1% to 79.4%). Conclusions: The FPIA had acceptable analytical performance during the study but compared to HPLC-MS overestimated everolimus in patient samples. This overestimation is probably due to calibration differences between the methods and cross-reactivity of the FPIA antibody with everolimus metabolites. The clinical importance of the observed overestimation by FPIA requires further investigation.

Objectives: Cyclosporin is an immunosuppressant drug with a narrow therapeutic window. Trough and 2-h post-dose blood samples are currently used for therapeutic drug monitoring in solid organ transplant recipients. The aim of the current study was to develop a rapid HPLC-tandem mass spectrometry (HPLC-MS) method for the measurement of cyclosporin in whole blood that was not only suitable for the clinical setting but also considered a reference method. Methods: Blood samples (50 mu L) were prepared by protein precipitation followed by C-18 solid-phase extraction while using d(12) cyclosporin as the internal standard. Mass spectrometric detection was by selected reaction monitoring with an electrospray interface in positive ionization mode. Results: The assay was linear from 10 to 2000 mu g/L (r(2) > 0.996, n = 9). Inter-day,analytical recovery and imprecision using whole blood quality control samples at 10, 30, 400, 1500, and 2000 mu g/L were 94.9-103.5% and

Tacrolimus is an immunosuppressant drug with a narrow therapeutic window and thus requires therapeutic drug monitoring. This study evaluates the suitability of the second-generation microparticle enzyme immunoassay (MEIA II) against a specific method, high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS), for the measurement of tacrolimus in both heart- and lung-transplant groups. A secondary objective was to investigate the effect of tacrolimus concentration on MEIA II measurement.The HPLC-MS assay was conducted as per our reported method and MEIA II performed according to manufacturer's instructions. Quality-control samples at 5, 11, and 22 microg/L were run in each batch to ensure assay integrity in both methods. Multiple trough samples from 18 heart patients (n = 126) and 17 lung patients (n = 203) were analyzed.The inter-batch imprecision and analytical recovery over the quality-control range by HPLC-MS (n = 12) was6% and 98.2% to 104%, respectively, and by MEIA II (n = 16)15% and 92.0% to 99.1%, respectively. The mean overestimation by MEIA II between the two methods for heart- and lung-transplant patient samples was found to be 9.9% (range: -37.4-45.4%) and 13.2% (range: -29.2-64.3%), respectively. Stratification of these data based on the tacrolimus concentration determined by MEIA II, yielded no statistically significant differences in bias between concentration subgroups within the clinically relevant range (p0.4). However, a statistically significant difference was detected between the highest concentration subgroup (20.0 microg/L) and lower concentration subgroups in both transplant populations (p0.05).This study suggests that where HPLC-MS is not available, MEIA II may be suitable for the therapeutic drug monitoring of tacrolimus in heart- and lung-transplant recipients. However, the clinical importance of the observed mean bias, considering the wide range in overestimation in heart- and lung-transplant patient samples, is yet to be determined.