Saudi Society for Clinical Chemistry

Beta Virsion

Copeptin

Copeptin is a 39-amino acid-long peptide derived from a pre-pro-hormone consisting of vasopressin, neurophysin II and copeptin. Arginine vasopressin (AVP), also known as the antidiuretic hormone (ADH), is involved in multiple cardiovascular and renal pathways and functions.

However, vasopressin measurements are not commonly used in clinical practice because of the biochemical features of the molecule: its small size and very short half-life make vasopressin testing quite complicated and labor-intensive.

The size and half-life of copeptin permit an easier immunological testing, compared to vasopressin, and hence copeptin is proposed as a reliable AVP surrogate. The clinical interest in copeptin testing is closely linked to the pathophysiological pathways in which vasopressin is involved : polydipsia-polyuria syndrome, hyponatremia, syndrome of inappropriate antidiuretic hormone secretion (SIADH) as well as heart failure and acute coronary syndrome.

In response to serum osmolality fluctuations, the kinetics of copeptine are comparable to those of vasopressin. For example, patients with an electrolyte disorders such as diabetes insipidus with very low levels of vasopressin also show very low levels of copeptin in blood plasma. On the other hand, patients suffering from syndrome of inappropriate antidiuretic hormone secretion show both high levels of vasopressin and copeptin.

Copeptin may be released much earlier than Troponin making the interpretation of their complementary kinetics a useful tool to rule-out acute myocardial infarction (AMI). It has been shown that the combination of a negative result of troponin together with a negative result of copeptin can rule-out AMI at emergency department presentation with a negative predictive value ranging from 95% to 100%. These results have been confirmed in a randomised controlled trial.

Studies have shown that vasopressin and copeptin can be useful as prognostic markers in heart failure. Patients presenting with high levels of vasopressin and copeptin have a worsened outcome.