Gender and renal function influence plasma levels of copeptin in healthy individuals

The present study sought to identify confounding factors for the interpretation of copeptin levels in healthy individuals. The natriuretic peptides are recognized as diagnostic and prognostic tools in HF (heart failure). Interpretation of BNP (brain natriuretic peptide) and NTproBNP (N-terminal pro-BNP) levels is multifaceted as their secretion is influenced by many variables. A newly identified glycopeptide called copeptin is comparable with the natriuretic peptides in the diagnosis and prognosis of HF and as a prognostic biomarker after AMI (acute myocardial infarction). Copeptin, derived from the C-terminal portion of the precursor to AVP (arginine vasopressin), is secreted stoichiometrically with vasopressin, hence it can be used as a surrogate marker of the AVP system. In the present study, 706 healthy volunteers were recruited from a local HF screening study. Participants with a history of cardiovascular disease and those with echocardiographic abnormalities were excluded from the study. Copeptin and NTproBNP levels were assayed using in-house immunoluminometric assays. Median copeptin levels were significantly higher in the male volunteers compared with the females [median (range): 4.3 (0.4-44.3) compared with 3.2 (1.0-14.8) pmol/l; P<0.001]. In males, copeptin was correlated with eGFR (estimated glomerular filtration rate; r(s)=-0.186, P<0.001). In females, the correlation of copeptin with eGFR was weak (r(s)=-0.097, P=0.095). DT (deceleration time) and left atrial size correlated with higher copeptin levels (r(s)=0.085, P=0.029 and r(s)=0.206, P<0.001 respectively). Only gender (P<0.001), eGFR (P<0.001), left atrial size (P=0.04) and DT (P=0.02) remained independently predictive of plasma copeptin. The present study suggests that gender and renal function specific partition values should be used to interpret copeptin values in future studies of this biomarker in HF or ischaemic heart disease.