PRELIMINARY EVALUATION OF A NEW CHEMILUMINESCENCE ASSAY (LIAISON® CYCLOSPORIN, DIASORIN LABORATORIES) ALLOWING BOTH C0 AND C2 CYLOSPORIN LEVEL DETERMINATION: COMPARISON WITH RIA METHOD.

P785 Cyclosporine (CsA) is widely used for maintenance immunosuppressive therapy both in adult and pediatric transplant recipients. Routine monitoring is generally assessed by trough concentration determination (C0). Recently, the 2-hours post-dose levels of CsA (C2) has been proposed as a better measurement to predict graft outcome and to prevent toxicity. However, using classical method, C2 determination requires external dilution which impairs the precision and practicability of the assay. Aims: This study assessed the performance characteristics of a new competitive chemiluminescence immunoassay (CLIA, DiaSorin® laboratories) for the determination of both C0 and C2 cyclosporine concentrations in whole blood on Liaison® analyser. Results were compared to RIA (Diasorin®) used in our laboratory as a reference method. Methods: This method, by contrast to others, needs no preliminary step (sample centrifugation or methanolic extraction) and CsA extraction is executed directly on whole blood. No dilution was required because only one calibration curve for C0 and C2 determinations was used allowing a linearity range from 30 to 2400 ng/ml. Results: Analytical performances show that total intra assay variation coefficients (CV’s) with high, medium and low values for Cyclosporin CLIA tested on Liaison® analyzer range from 7.6 to 11.3% while between day imprecision was 11% (15.2, 11.5 and 6.5%). The coefficient of linearity estimated between 30 to 2400 ng/ml yielded r= 0.997. Recoveries were checked by adding Sandimmun® to CSA free blood in order to reach following concentrations : 50, 100, 200, 400, 600, 800, 1000 and 2000 ng/ml. Mean recovery was 89% for RIA and 86% for Liaison® respectively and r2 was 0.97 for RIA and 0.96 for Liaison®. 236 whole blood samples (31% females, 69% males, mean age 45±17 years) were collected from patients admitted to Nephrology department of Lapeyronie hospital (Montpellier, France). Samples used for the between-method correlations ranging from 0 to 3244 ng/ml. The comparative study between CLIA-Cyclosporine and RIA method values led to correlations coefficients > 0.90 (CLIA = 0.825 RIA + 21.611; r2>0.90). Conclusions: In conclusion, the Liaison® cyclosporine kit is an alternative to radioisotopic method which allowed both C0 and C2 determination without any preanalytical step. The chemiluminescence method demonstrated good analytical performances and good practicability in routine use.