The EMIT ® cyclosporine assay: Development of application protocols for the Boehringer Mannheim Hitachi 911 and 917 analyzers

Objective: The purpose of this work was to develop applications for the EMIT ® Cyclosporine (CsA) Assay on the Hitachi 911 and 917 analyzers. Methods and Results: Instrument settings were optimized to arrive at the following assay characteristics on the Hitachi 917. Limit of sensitivity was 50 μg/L. Intra-assay coefficients of variation (CV) were 8.1% ( n = 20; x = 62 μg/L) and 4.2% ( n = 20; x = 315 μg/L), while interassay CVs were 13.0% ( n = x = 73 μg/L) and 5.7% ( n = 43; x = 391 μg/L. Recoveries of 95–104% were obtained by spiking aliquots of 3 whole blood patient pools of known CsA concentrations with CsA. Serial dilutions of 3 patient specimens demonstrated linear relationships between expected and actual CsA concentrations ( r = 0.99, 0.99, 0.98; regression lines: y = 1.19x − 17.1; y = 0.75x + 18.0; y = 1.01x + 3.7). Specimen carryover was not evident. Calibration stability is at least 10 days. Comparable assay characteristics were found for the Hitachi 911. Sequentially-collected 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 ® on the Hitachi 917 and also by fluorescence polarization immunoassay (FPIA) and high performance liquid chromatography (HPLC). The following linear regression equations were produced for the renal [EMIT ® = 0.801 (TD x ®) + 4.98, r = 0.91, Sy/x = 32, n = 37; EMIT ® = 0.887 (HPLC) + 56, r = 0.87, Sy/x =38, n = 37]; liver (TD x ®) − 27, r = 0.94, Sy/x = 42, n = 37; EMIT ® = 0953 (HPLC) + 44, r = 0.89, Sy/x = 57, n = 37] and heart EMIT ® = 0.820 (TD x ®) − 24, r = 0.94, Sy/x = 31, n = 45; EMIT ® = 0.956 (HPLC) + 54, r = 0.91, Sy/x =38, n = 45] patient samples. FPIA values average 32% more than EMIT ®-derived CsA concentrations on the Hitachi 917, which in turn averaged 15% more than HPLC values. 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 ® and by FPIA compared to HPLC. Although CsA concentrations within most patients were significantly higher ( p < 0.05) by EMIT ® 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 ® CsA Assay on two highly automated, random access instruments, the Hitachi 911 and Hitachi 917, enhances the versatility of the immunoassa