Comparison of NT-proCNP and CNP plasma levels in heart failure, diabetes and cirrhosis patients.

C-type natriuretic peptide (CNP) plasma levels are extremely low and a pre-analytical phase is necessary to assay plasma CNP concentrations. Amino-terminal CNP (NT-proCNP) circulates at higher concentrations than CNP, allowing a direct assay and the use of smaller amounts of plasma. Aim of this study was to evaluate the analytical performance of a direct NT-proCNP assay and to measure its plasma levels in heart failure (CHF), diabetes and chirrosis patients. NT-proCNP and CNP were measured in 130 CHF, 19 patients with diabetes, 24 with hepatic cirrhosis and 73 controls. Plasma NT-proCNP was higher in all the clinical conditions studied (controls:45.5 ± 1.84 pg/ml, CHF:67.09 ± 7.36, diabetes:51.5 ± 5.75 cirrhosis:78.4 ± 19.9; p = 0.034, p = 0.04 controls vs. CHF and cirrhosis, respectively) and in CHF NT-proCNP concentration showed a significant increase as a function of clinical severity. By comparison of ROC curves, CNP assay resulted better associated with disease than NT-proCNP assay in all the different clinical conditions probably due to different release and clearance. The determination of NT-proCNP adds a piece of information to better understanding the molecular mechanisms at the basis of CNP action in different diseases. Due to its higher analytical feasibility, this determination could become widespread in clinical biochemistry laboratories and serve as a complementary marker of disease conditions.