Age effect on whole blood cyclosporine concentrations following oral administration in children with nephrotic syndrome
Cyclosporine (CyA) has a narrow therapeutic index. Determination of CyA concentrations correlate with rejection or adverse effects like nephropathy. Cyclosporine is assayed based on either chromatographic or many different immunoenzymologic techniques. The investigators evaluated a new heterogeneous immunoassay of CyA on RxL Dimension. The pretreatment step is automatically performed in the apparatus. Linearity, intra- and interday precision, limit of quantification, dilutions, and stability of the equipment were compared with the EMIT method for patient determinations. The heterogeneous immunoassay showed a good linearity between 0 and 500 ng/mL, and intra- and inter-day precision with a coefficient of variation below 9.2%. The investigators observed reproducible and accurate dilutions of high concentrations (500 to 2000 ng/mL). The correlation with the EMIT technique was valid: ACMIA = 0.964 EMIT + 0.156 (r = .96) for different types of transplant (n = 116). Finally, this new system improves the determination of CyA concentrations.