Evaluation of the immunotech cyclosporine direct radioimmunoassay for the determination of whole-blood cyclosporine in renal transplant patients

Therapeutic drug monitoring (TDM) of cyclosporine (CsA) has been an accepted as an essential tool in the management of solid organ transplant recipients. The authors evaluated a new CsA method, Immunotech cyclosporine direct radioimmunoassay (Beckman Coulter, Prague, Czech Republic), for the measurement of whole-blood CsA concentrations. The performance was compared with CEDIA Plus (D method as well as group mean data for HPLC and other immunoassays available from the International CsA Proficiency Testing Program (www.bioanalytics.co.uk). Regression analysis of patient samples gave a relationship of RIA = 1.0822 CEDIA(+) + 69.84 (r(2) = 0.933). External CsA-spiked proficiency-testing (PT) samples gave a regression equation of RIA = 0.9672 CEDIA(+) + 4.99 (r(2) = 0.996). The correlation with the CEDIA Plus' method using patient specimens (hence, including CsA metabolites) suggested that the test RIA method possibly had slightly inferior specificity for parent CsA. The results suggest that the Immunotech cyclosporine direct RIA kit is suitable for the measurement of whole-blood CsA concentrations and maintained clinically acceptable analytic precision and accuracy, displaying CVs of less than 15% and biases of less than 10%. The PT program CsA-metabolite-free samples showed that calibration between methods was comparable with the possible exception of mFPIA/TDx.