Abstract

Background: The purpose of this study was to evaluate relative performances of the ARCHITECT and DIMENSION immunoassays, the first requiring preanalytical pretreatment, the last one not.
Material/Methods: Method comparison analyses were performed by testing specimens from transplant recipients. The functional sensitivities (LOQ) of the ARCHITECT and DIMENSION were assessed by testing whole blood specimens spiked with tacrolimus or cyclosporine, run in replicates of 10 on two consecutive days on both instruments. Metabolite cross-reactivity was measured directly in whole blood containing a target concentration of 200 ng/mL cyclosporine and 1,000 ng/mL purified cyclosporine metabolites (AM1, AM1c, AM4N, AM9, AM19). Hematocrit levels were recorded.
Results: The following results were obtained in patient correlation studies: ARCHITECT vs DIMENSION tacrolimus (n=197) Spearman r=0.95, y=0.98x - 0.27 and an average bias of -0.46 ng/mL; ARCHITECT vs DIMENSION cyclosporine (n=95) Spearman r=0.94, y=x - 20 and an average bias of -20.8ng/mL. The LOQ (20%CV) for tacrolimus was 0.6 ng/mL vs 3.1 ng/mL on the ARCHITECT vs DIMENSION, respectively. For cyclosporine these values were 12.1 ng/mL vs 28 ng/mL, respectively for ARCHITECT vs Dimension. Statistical analysis of the 3 ng/mL functional sensitivity panel yielded the following results: ARCHITECT, mean =3.03 ng/mL (95% CI=2.71-3.36); DIMENSION, mean =2.80 ng/mL (95% CI=1.44-4.15). Cyclosporine metabolite cross-reactivity ranged from -0.8% up to 2.2% for the ARCHITECT and from -0.1 up to 6.4% for the DIMENSION, respectively. Hematocrit did not affect any of these assays.
Conclusions: Both assays displayed satisfactory analytical performances. However, from these data, it is suggested that the preanalytical steps involved in the ARCHITECT as says might contribute positively in their analytical performances (particularly the LOQ) as compared to the fully automated DIMENSION.

Keywords: -----, bladder tissue, electrical impedance, first record-able reading, optimal probe pressure, Tacrolimus