The V-Twin system (Dade Behring Laboratories): A useful tool for immunosuppressive drug monitoring

The Emit® 2000 Cyclosporine Specific Assay, Extended Range: development of an application protocol for the V-Twin® analyzer

We evaluated a new protocol for measurement of cyclosporine A (CsA) 2 H after dose (C2) on the V-Twin® analyzer. Imprecision, recovery, and linearity were determined using CsA-spiked blood pools. Accuracy was evaluated using specimens from renal, cardiac, and liver transplant patients, and results were compared with those from liquid chromatography-tandem mass spectrometry (LC-MS/MS) and the Abbott TDx®/TDxFLx® assay. Cross-reactivity and interferences were assessed in the presence of 800 ng/mL CsA. Imprecision coefficients of variation were 3.3%-4.8% (within run) and 5.9%-8.7% (total). Recovery was within 10% of the expected values. Linearity was 350-2,000 ng/mL. Calibration was stable for ≥ 2 weeks. Method comparison showed regression statistics: V-Twin® = 1.01 × LC tandem MS + 36.1, r = 0.971; V-Twin® = 1.13 × Abbott - 92.4, r = 0.969. Metabolite cross-reactivity and interference (endogenous substances and drugs) were within ±10%. The C2 protocol on the V-Twin® analyzer provides acceptable assay performance and accurate determination of whole blood CsA drawn at 2 H after dose.

Monitoring of C0 and C2 blood concentrations of cyclosporine on the Roche Hitachi 902 analyzer

This work provided parameters to perform the widely used enzyme multiplied immunoassay technique (Emit) cyclosporine assay on a Hitachi 902 analyzer. Instrument settings were optimized to arrive at assay characteristics regarding precision, linearity, and lower limit of quantitation among 105 samples from renal transplant recipients receiving cyclosporine. We compared successive results with Emit on a Cobas Integra 400 analyzer with HPLC-UV. We validated a quantitation range of 20-500 ng/mL. For all parameters tested total imprecision <5%. Calibration stability was at least 30 days. The reagent cartridge in the instrument was stable for 2 months between runs. We observed good correlations with other analytical methods. The following equations were obtained: Hitachi 902 = 0.984 Cobas Integra + 2.097; r = 0.998 and Hitachi 902 = 1.019 LC-UV + 3.143; r = 0.974. The mean bias was 1.68% for C0 and 0.02% for C2 concentrations between Hitachi 902 and Cobas Integra 400. Overestimations of 5.61% for C0 and 8.81% for C2 levels assayed with Emit Hitachi 902 were observed compared with LC-UV. The proposed, validated protocol enhanced the versatility of the Emit assay for routine therapeutic drug monitoring. The Hitachi 902 analyzer is an acceptable option for evaluation of C0 and C2 blood cyclosporine concentrations in transplant recipients.