THE EMIT(R) CYCLOSPORINE ASSAY - DEVELOPMENT OF APPLICATION PROTOCOLSFOR THE BOEHRINGER-MANNHEIM-HITACHI-911-ANALYZERS AND 917-ANALYZERS

Objective: The purpose of this work was to develop applications for th e EMIT(R) Cyclosporine (CsA) Assay on the Hitachi 911 and 917 analyzer s. Methods and Results: Instrument settings were optimized to arrive a t the following assay characteristics on the Hitachi 917. Limit of sen sitivity was 50 mu g/L. Intra-assay coefficients of variation (CV) wer e 8.1% (n = 20; (x) over bar = 62 mu g/L) and 4.2% (n = 20; (x) over b ar = 315 mu g/L), while interassay CVs were 13.0% (n = (x) over bar = 73 mu g/L) and 5.7% (n = 43; (x) over bar = 391 mu g/L). Recoveries of 95-104% were obtained by spiking aliquots of 3 whole blood patient po ols of known CsA concentrations with CsA. Serial dilutions of 3 patien t specimens demonstrated linear relationships between expected and act ual CsA concentrations (r= 0.99, 0.99, 0.98; regression lines: y = 1.1 9 x -17.1; y = 0.75 x +18.0; y = 1.01 x +3.7). Specimen carryover was not evident. Calibration stability is at least 10 days. Comparable ass ay characteristics were found for the Hitachi 911, Sequentially-collec ted trough whole blood specimens from renal (n = 3), liver (n = 3) and heart (n = 4) transplant patients prescribed CsA were collected up to 78 days post-transplant and analyzed by EMIT(R) on the Hitachi 917 an d also by fluorescence polarization immunoassay (FPIA) and high perfor mance liquid chromatography (HPLC). The following linear regression eq uations were produced for the renal [EMIT(R) = 0.801 (TDx(R)) + 4.98, r = 0.91, Sy/x = 32, n = 37; EMIT(R) = 0.877 (HPLC) + 56, r = 0.87, Sy i/= 38, n = 37]; liver [EMIT(R) = 0.808 (TDx(R)) - 27, r = 0.94, Sy/x = 42, n = 37; EMIT(R) = 0.953 (HPLC) + 44, r = 0.89, Sy/x = 57, n = 37 ] and heart [EMIT(R) = 0.820 (TDx(R)) -24, r = 0.94, Sy/x = 31, n = 45 ; EMIT(R) = 0.956 (HPLC) + 54, r = 0.91, Sy/x = 38, n = 45] patient sa mples. FPIA values average 32% more than EMIT(R)-derived CsA concentra tions on the Hitachi 917, which in turn averaged 15% more than HPLC va lues. In addition, these levels were compared intra-individually. CsA concentrations within all patients were significantly higher (p < 0.05 , paired t-test) by FPIA compared to EMIT(R) and by FPIA compared to H PLC. Although CsA concentrations within most patients were significant ly higher (p < 0.05) by EMIT(R) compared to HPLC, levels determined in 4 transplant patients (1 renal, 1 liver, 2 heart) were not different. Conclusion: Development of applications for the EMIT(R) CsA Assay on two highly automated, random access instruments, the Hitachi 911 and H itachi 917, enhances the versatility of the immunoassay for routine th erapeutic drug monitoring of this immunosuppressant in the clinical se tting.