Background: Arginine vasopressin (AVP) is a key regulator of water balance, but its instability makes reliable measurement difficult and precludes routine use. We present a method for quantifying AVP release by use of copeptin, a glycopeptide comprising the C-terminal part of the AVP prohormone. Methods: We measured copeptin in 50-L serum and plasma samples from healthy individuals and from critically ill patients with sepsis. Our sandwich immunoluminometric assay used 2 polyclonal antibodies to amino acids 132-164 of pre-provasopressin. Results: The assay yielded results within 3 h. The analytical detection limit was 1.7 pmol/L, and the interlaboratory CV was <20% for values >2.25 pmol/L. The assay was linear on dilution of the analyte. Ex vivo copeptin stability (<20% loss of analyte) for at least 7 days at room temperature and 14 days at 4°C was shown for serum and EDTA-, heparin-, and citrate plasma. Copeptin (median, 4.2 pmol/L; range, 1-13.8 pmol/L) was detectable in 97.5% of 359 healthy individuals and was not associated with age. Median concentrations were considerably higher in men than women, increased significantly after exercise, and were influenced by fasting and water load. Copeptin was significantly (P <0.001) increased in 60 critically ill patients with sepsis (median, 79.5 pmol/L; range, 10.6 -228.0 pmol/L). The correlation between copeptin and AVP for 110 samples was r ‫؍‬ 0.78 (P <0.0001). Conclusions: Copeptin is stable for days after blood withdrawal and can be quickly and easily measured.

The additional use of copeptin seems to allow a rapid and reliable rule out of AMI already at presentation and may thereby obviate the need for prolonged monitoring and serial blood sampling in the majority of patients. (Advantageous Predictors of Acute Coronary Syndromes Evaluation [APACE]; NCT00470587).

Blood pressure is a heritable trait, but no common genetic variants contributing to blood pressure in humans have been definitively established. Natriuretic peptides (NP) have blood pressure-lowering properties. Genotyping SNPs at the NPPA/NPPB locus in 14,743 individuals of European ancestry identified associations of plasma atrial natriuretic peptide with rs5068 (P=8×10−70), rs198358 (P=8×10−30), and rs632793 (P=2×10−10), and of plasma B-type natriuretic peptide with rs5068 (P=3×10−12), rs198358 (P=1×10−25), and rs632793 (P=2×10−68). In 29,717 individuals, the alleles of rs5068 and rs198358 related to increased circulating NP concentrations were associated with lower systolic (P=2×10−6 and 6×10−5, respectively) and diastolic blood pressure (P=1×10−6 and 5×10−5), and reduced odds of hypertension (odds ratio 0.85, 95% confidence interval, 0.79–0.92, P=4×10−5; odds ratio 0.90, 95% confidence interval, 0.85–0.95, P=2×10−4, respectively). Common genetic variants related to circulating NP concentrations contribute to inter-individual variation in blood pressure and hypertension.

Background: Adrenomedullin (ADM) is a potent vasodilatory peptide, and circulating concentrations have been described for several disease states, including dysfunction of the cardiovascular system and sepsis. Reliable quantification has been hampered by the short half-life, the existence of a binding protein, and physical properties. Here we report the technical evaluation of an assay for midregional pro-ADM (MR-proADM) that does not have these problems. Methods: MR-proADM was measured in a sandwich immunoluminometric assay using 2 polyclonal antibodies to amino acids 45-92 of proADM. The reference interval was defined in EDTA plasma of 264 healthy individuals (117 male, 147 female), and increased MRproADM concentrations were found in 95 patients with sepsis and 54 patients with cardiovascular disease. Results: The assay has an analytical detection limit of 0.08 nmol/L, and the interassay CV was <20% for values >0.12 nmol/L. The assay was linear on dilution with undisturbed recovery of the analyte. EDTA-, heparin-, and citrate-plasma samples were stable (<20% loss of analyte) for at least 3 days at room temperature, 14 days at 4°C, and 1 year at ؊20°C. MR-proADM values followed a gaussian distribution in healthy individuals with a mean (

Background-The role of the vasopressin system after acute myocardial infarction is unclear. Copeptin, the C-terminal part of the vasopressin prohormone, is secreted stoichiometrically with vasopressin. We compared the prognostic value of copeptin and an established marker, N-terminal pro-B-type natriuretic peptide (NTproBNP), after acute myocardial infarction. .003) were significant independent predictors of death or heart failure at 60 days. The area under the receiver operating characteristic curves for copeptin (0.75) and NTproBNP (0.76) were similar. The logistic model with both markers yielded a larger area under the curve (0.84) than for NTproBNP (PϽ0.013) or copeptin (PϽ0.003) alone, respectively. Cox modeling predicted death or heart failure with both biomarkers (log copeptin [hazard ratio, 2.33], log NTproBNP [hazard ratio, 2.70]). In patients stratified by NTproBNP (above the median of Ϸ900 pmol/L), copeptin above the median (Ϸ7 pmol/L) was associated with poorer outcome (PϽ0.0005). Findings were similar for death and heart failure as individual end points. Conclusions-The vasopressin system is activated after acute myocardial infarction. Copeptin may predict adverse outcome, especially in those with an elevated NTproBNP (more than Ϸ900 pmol/L). Methods and Results-In

Background Animal studies suggest that the arginine vasopressin (AVP) system may play a role in glucose metabolism, but data from humans are limited. Methods and Results We analysed plasma copeptin (copeptin), a stable C-terminal fragment of the AVP pro-hormone. Using baseline and longitudinal data from a Swedish population-based sample (n=4742, mean age 58 years, 60% women), we examined the association of increasing quartiles of copeptin (lowest quartile as reference) with prevalent diabetes at baseline, insulin resistance (top quartile of fasting plasma insulin among non-diabetic subjects), and incident diabetes on long-term follow up using multivariable logistic regression. New-onset diabetes was ascertained through 3 national and regional registers. All models were adjusted for clinical and anthropometric risk factors, cystatin C, and C-reactive protein. In cross-sectional analyses, increasing copeptin was associated with prevalent diabetes (P=0.04) and insulin resistance (P<0.001). During 12.6 years of follow up 174 subjects (4%) developed new-onset diabetes. The odds of developing diabetes increased across increasing quartiles of copeptin, even after additional adjustment for baseline fasting glucose and insulin (adjusted odds ratios 1.0, 1.37, 1.79, and 2.09; P for trend =0.004). The association with incident diabetes remained significant in analyses restricted to subjects with fasting whole blood glucose <5.4 mmol/L at baseline (adjusted odds ratios 1.0, 1.80, 1.92, and 3.48; P=0.001). Conclusions Elevated copeptin predicts increased risk for diabetes, independent of established clinical risk factors, including fasting glucose and insulin. These findings could have implications for risk assessment, novel anti-diabetic treatments, and metabolic side effects from AVP system modulation.

In triage of chest pain patients, determination of copeptin in addition to troponin improves diagnostic performance, especially early after CPO. Combined determination of troponin and copeptin provides a remarkable negative predictive value virtually independent of CPO time and therefore aids in early and safe rule-out of myocardial infarction.

The prohormone of atrial natriuretic peptide (proANP) is a polypeptide of 126 amino acids. Mature atrial natriuretic peptide (ANP) consists of amino acids 99 -126 and comprises 98% of the natriuretic peptides in the circulation (1 ). The N-terminal portion of proANP, termed proANP1-98 or NT-proANP, has a much longer half-life than mature ANP and has therefore been suggested to be a more reliable analyte for measurement than mature ANP (2 ). In addition to other established indications, proANP has recently gained much interest as a potential new marker in the field of sepsis (3 ), emphasizing the need for a reliable assay for this molecule.All sandwich immunoassays developed for proANP to date use an antibody against the N-terminal region of proANP1-98 combined with a second antibody against either the midregion (4 ) or C-terminal region (5, 6 ). However, under certain conditions, the N-terminal region might be minimally accessible for antibody binding (7,8 ). Despite the described long half-life of proANP, results from various competitive immunoassays as well as HPLC analyses indicate that proANP1-98 can be subject to further fragmentation (9, 10 ).We developed a new sandwich immunoassay for midregional proANP (amino acids 53-90; EDTA-plasma samples were collected at a blood bank (Red Cross) from 325 consecutive healthy blood donors (age range, 18 -67 years; 52.9% male) without clinical evidence of acute disease or a history of chronic illness. Blood donors with risk factors for heart failure were not enrolled in the study. Written consent was obtained from all donors.For the proANP assay, tubes were coated with affinitypurified polyclonal sheep antibodies specific for amino acids 73-90 (GRGPWDSSDRSALLKSKL) of the molecule (Fig. 1A). Coating of the antibody was done for 20 h on polystyrene tubes (1.5 g/tube) in 0.3 mL of buffer (10 mmol/L Tris-HCl, pH 7.8; 10 mmol/L NaCl). Tubes were blocked with 10 mmol/L sodium phosphate buffer containing 30 g/L of the polysaccharide Karion FP (Merck AG) and 5 g/L protease-free bovine serum albumin (Sigma), pH 6.8, and were lyophilized. A polyclonal sheep antibody specific for another part of proANP was used as tracer. This antibody was raised to peptide 53-72 (PEVP-PWTGEVSPAQRDGGAL) of proANP and was affinity purified on a peptide-sulfolink column. After purification, the antibody was labeled with acridinium ester as follows: 100 g of antibody in 20 mmol/L sodium phosphate buffer, pH 8.0, was incubated for 20 min at room temperature with 10 L of acridinium ester (1 g/L in acetonitrile; Hoechst AG). Labeled antibody was purified by HPLC with a Knauer hydroxyapatite column (buffer gradient, 1-500 mmol/L potassium phosphate, pH 6.8; flow rate, 0.8 mL/min).Plasma proANP was measured as follows: 20 L of patient sample (EDTA plasma) or calibrator was added in duplicate to antibody-coated tubes containing 50 mmol/L sodium phosphate buffer, pH 7.5, and incubated for 2 h at room temperature. After five washes with 2 mL of standard LUMItest © washing buffer (B.R.A.H.M.S AG), 200 L of t...