Comparison of cyclosporin G (Nva2-cyclosporin) concentrations measured in whole blood by monoclonal fluorescence polarization immunoassay, monoclonal radioimmunoassay, and HPLC.

Two commercial monoclonal immunoassays for monitoring cyclosporin A were used to measure whole-blood concentrations of the immunosuppressant cyclosporin G (CsG) in renal transplant patients. We performed a three-way comparison of these two immunoassays and HPLC. Although the two immunoassays agreed favorably, both the monoclonal fluorescence polarization immunoassay and the monoclonal RIA yielded higher CsG results for patients' specimens than did the liquid-chromatographic assay. The experimental data indicate that the observed differences are most likely due to the cross-reactivity of CsG metabolites in the immunoassays.