Copeptin, a Stable Peptide of the Arginine Vasopressin Precursor, is Elevated in Hemorrhagic and Septic Shock

Arginine vasopressin (AVP) levels are increased in hemorrhagic and septic shock. Measurement of AVP levels has limitations due to its short half-life and cumbersome detection method. Copeptin is a more stable peptide derived from the same precursor molecule. We evaluated the plasma copeptin concentration in two independent studies: first, in an experimental baboon model of hemorrhagic shock, and second, in a prospective observational study of 101 consecutive critically ill patients at a university hospital. Copeptin was measured with a newly developed sandwich immunoassay using two polyclonal antibodies to the C-terminal region (amino acid sequence 132-164) of pre-pro-AVP. Copeptin concentrations in hemorrhagic shock increased markedly from median (range) of 7.5 [2.7-13) to 269 pM (241-456 pM). After reperfusion, copeptin levels dropped within hours to a plateau of 27 pM (15-78 pM). In the critically ill patient cohort, copeptin values increased significantly with the severity of the disease and were in patients without sepsis [27.6 pM [2.3-297 pM]), in sepsis [50.0 pM [8.5-268 pM]), in severe sepsis [73.6 pM [15.3-317 pM]), and in septic shock [171.5 pM (35.1-504 pM] compared with 4.1 pM (1.0-13.8 pM) in healthy controls (P for all vs. controls <0.001). On admission, circulating copeptin levels were higher in nonsurvivors (171.5 pM, 46.5-504.0 pM) as compared with survivors (86.8 pM, 8.5-386.0 pM; P = 0.01). Copeptin levels correlated with basal cortisol levels (r = 0.42; P < 0.001) and osmolality (r = 0.42; P < 0.001). In a logistic regression model including other covariates besides copeptin (e.g., determinants of fluid status) on survival, serum copeptin levels were the only independent significant predictor of outcome (P = 0.03). Copeptin concentrations are elevated in hemorrhagic and septic shock. Copeptin was higher on admission in nonsurvivors as compared with survivors, suggesting copeptin as a prognostic marker in sepsis. The availability of a reliable assay for the measurement of AVP release can also prove useful for the assessment of fluid and osmosis status in various diseases.