Background: Immunoassays used for the measurement of cyclosporine (CsA) usually show cross-reactivity for CsA metabolites, usually resulting in unacceptable bias.
Methods: To assess the performance of different immunoassays, CsA concentrations were analyzed in 132 samples using ACMIA, EMIT-VIVA, CEDIA-PLUS, and HPLC. Samples were collected from kidney transplant patients monitored with the traditional blood CsA trough level (C0, n=73) and the new sampling at 2-h post CsA dosing (C2, n=59).
Results: Overall, the correlations between HPLC and other methods were good (r values ranging from 0.85 to 0.97). The use of C2 concentrations to monitor CsA exposure were associated with an overall better performance of all the immunoassays as compared with C0 values. However, none of the immunoassays agreed with the guidelines proposed in the Lake Louis Consensus Conference. Of note, the CEDIA-PLUS was the only that provided a linear relationship with HPLC for both sampling times. A false positive case associated with ACMIA was also documented in blood samples from a patient withdrawn from CsA for 1 month.
Conclusion: These data suggest that the performance of some of the most used immunoassays is not satisfactory, eventually leading to incorrect therapeutic decision guided by erroneous CsA monitoring.