RELATIONSHIP BETWEEN CNP AND NT-PROCNP ASSAY IN DISEASES CHARACTERIZED BY ENDOTHELIAL DYSFUNCTION

Background. C-type natriuretic peptide (CNP) plays a central role in the control of vascular tone and in several clinical conditions characterized by endothelial dysfunction. Amino- terminal CNP (NT-proCNP), circulates at higher concentrations than CNP allowing a direct assay and the use of smaller amounts of plasma. Aim and methods. To evaluate the analytical performance of a direct ELISA for NT-proCNP (Biomedica Gruppe-Pantec) and to compare its plasma levels with those of CNP in controls (n=37), CHF (n=130), diabetes (n=19) and cirrhosis (n=24) patients. Results. As to NT-proCNP assay, between and within assay variabilities were 15% and 8% respectively (sensitivity 0.34±0.03 pg/tube). Higher plasma levels of CNP and NT- proCNP were found in diabetes: 7.8±0.4; 51.5±5.7, cirrhosis: 5.0±0.5; 78.4±19.9 and CHF: 7.8±0.4; 67.0±7.3 pg/ml, respect to the controls (2.4±0.1; 37.4±1.9 pg/ml). A significant correlation was observed between NT-proCNP and CNP (r= 0.32, p<0.0001) considering the patients as a whole. In CHF the concentrations increased as a function of the severity. Both CNP and NT-proCNP significantly correlated with IL-6 (r=0.26, p=0.008; r=0.395, p<0.0001), noradrenaline (r=0.35, p=0.0005; r=0.369, p=0.0002), BNP (r=0.57, p<0.0001; r=0.216, p=0.037) and NT-proBNP (r=0.53, p<0.0001; r=0.25 p=0.035). No difference in diagnostic accuracy (ROC analysis) between CNP and BNP were found. Conclusions. Although the diagnostic accuracy of this determination has to be evaluated on a larger number of subjects, NT-proCNP assay results more easy to perform of CNP and suitable for reliably detect changes in NT-proCNP plasma levels as a function of different clinical conditions and severity.