Arginine vasopressin (AVP) and copeptin are derived from the same precursor peptide. Copeptin has been proposed as a more stable, potentially superior, surrogate marker of AVP in the assessment of water balance disorders. Both copeptin and AVP are responsive to osmotic stimuli and increase in response to water deprivation. Copeptin increases gradually with fasting and water deprivation and declines rapidly after intake of water and /or food.
The determination of the underlying disease pathology in patients with polyuria and altered plasma osmolality is often difficult. Polyuria can be related to insufficient AVP (central DI), reduced sensitivity to AVP (nephrogenic DI), or excessive water intake. Measurement of copeptin concentration has been shown to be useful in the investigation of these AVP related disorders.
Morning sample (without water restriction) unless otherwise stated by clinician.
If overnight - Frozen
Copeptin measurement is indicated in the investigation of diabetes insipidus (DI) and primary polydipsia (PP) in conjunction with osmolality and hydration status. In patients with confirmed polyuria (>50mL/Kg/d):
A non-water deprived non-fasting copeptin level of greater than or equal to 21.4 pmol/L is highly sensitive and specific for nephrogenic diabetes insipidus.
A stimulated copeptin (sodium >147 mmol/L following water deprivation) > 4.9 pmol/L PP likely and less than or equal to 4.9 pmol/L partial central DI likely (94% specificity and 94% sensitivity).
Following arginine stimulation, copeptin less than or equal to 3.8 pmol/L supports central DI and >3.8 pmol/L PP (92% specificity and 93% sensitivity).
Time-Resolved Amplified Cryptate Emission (TRACE).
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Cautions: severe sepsis, septic shock, lower respiratory infections, chronic obstructive pulmonary disease (COPD) and cardiovascular disease, ie, chronic heart failure may increase copeptin concentrations.
Winzeler B, Cesana-Nigro N, Refardt J, Vogt D.R, Imber C, Morin B, Popovic M, Steinmetz M, Sailer C.O, Szinnai G, Chifu I, Fassnacht M, Christ-Crain M. Arginine-stimulated copeptin measurements in the differential diagnosis of diabetes insipidus: A prospective diagnostic study. Lancet. 2019 Aug 17;394 (10198):587-595.
Keller T, Tzikas S, Zeller T, et al: Copeptin improves early diagnosis of acute myocardial infarction. J Am Coll Cardiol. 2010 May 11; 55 (19):2096-2106.
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