Copeptin
Clinical Background:
The Brahms CT-proAVP assay measures the C-terminal precursor fragment of arginine vasopressin (AVP), otherwise known as copeptin. Copeptin is released on an equimolar basis with AVP and therefore m...
The Brahms CT-proAVP assay measures the C-terminal precursor fragment of arginine vasopressin (AVP), otherwise known as copeptin. Copeptin is released on an equimolar basis with AVP and therefore measurement of serum/plasma copeptin provides a surrogate measure of AVP concentrations.
The clinical value of measuring serum copeptin is in the differential diagnosis of polyuria/polydipsia syndromes. The differentiation of AVP deficiency (cranial diabetes insipidus) from primary polydipsia can be made by direct measurement of serum copeptin during the controlled osmotic stress of a hypertonic 5% sodium chloride infusion. The test should not be carried out in those patients with a significant history of cardiac failure, seizures or a history of significant stroke disease. Monitoring of serum sodium during the test can guide hypertonic saline infusion and reduce the risk of excessive hypernatraemia. The diagnostic utility of copeptin measurement during the water deprivation test is often low, unless there is a significant osmotic stimulus (i.e. serum sodium of ~150 mmol/L). Patients with AVP resistance (nephrogenic diabetes insipidus)typically have higher copeptin concetrations for basal/random samples, although it should be noted that other factors such as stress, intercurrent illness and low GFR can also lead to increased copeptin.
Test Details
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Discipline:
Biochemistry
Biochemistry
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Specimen Container Adult:
serum (lithium heparin also accepted)
serum (lithium heparin also accepted)
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Specimen Container Paediatric:
serum (lithium heparin also accepted)
serum (lithium heparin also accepted)
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Minimum Volume Adult:
1 mL blood
1 mL blood
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Minimum Volume Paediatric:
1 mL blood
1 mL blood
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Special Requirement:
Copeptin measurements are of most value when taken under an osmotic stimulus. Please include clinical details and concurrent osmolality results with all requests.
Copeptin measurements are of most value when taken under an osmotic stimulus. Please include clinical details and concurrent osmolality results with all requests.
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Sample Stability:
Unseparated: Same day
Separated: 7 days at 20-25°C 14 days at 4-8°CUnseparated: Same day
Separated: 7 days at 20-25°C 14 days at 4-8°C -
Transport Requirements:
Ambient
Ambient
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Interpretation:
Serum/plasma measurements from saline infusions can be interpreted with reference to a plot of copeptin vs osmolality in healthy individuals. A graphical report is included with all sample series c...
Read MoreSerum/plasma measurements from saline infusions can be interpreted with reference to a plot of copeptin vs osmolality in healthy individuals. A graphical report is included with all sample series collected during saline infusion. Patients with AVP deficiency (central DI) do not typically acheive a copeptin greater than 4.9 pmol/L during osmotic stimulation (serum sodium ≥150 mmol/L).
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Reference Ranges:
No single reference range is applicable as copeptin varies according to plasma osmolality in normal individuals. An interpretive comment will be included with each report.
No single reference range is applicable as copeptin varies according to plasma osmolality in normal individuals. An interpretive comment will be included with each report.
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Factors Affecting Result:
Heterophilic antibodies can interfere with immunoassays.
Heterophilic antibodies can interfere with immunoassays.
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Referenced Documents:
Timper K et al. Diagnostic accuracy of copeptin in the differential diagnosis of the polyuria-polydipsia syndrome: A prospective multicentre study. JCEM 2015 doi:10.1210/jc.2014-4507.
Timper K et al. Diagnostic accuracy of copeptin in the differential diagnosis of the polyuria-polydipsia syndrome: A prospective multicentre study. JCEM 2015 doi:10.1210/jc.2014-4507.
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Routine Contact Name:
Duty Biochemist
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Routine Telephone:
Freeman: 0191 244 8889
RVI: 0191 282 9719
Freeman: 0191 244 8889
RVI: 0191 282 9719
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Routine Email:
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Specialist Test:
Yes
Yes
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Specialist Contact Name:
Endocrine Lab
Endocrine Lab
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Specialist Telephone:
0191 282 4025
0191 282 4025