Laboratory: Clinical Biochemistry  (SENDOUTS)
Test Name:
COPEPTIN - (P)
Test Code: MISC
Clinical Information:
Alternate Name(s):ADH, Antidiuretic hormone, vasopressin, arginine vasopressin, AVP, ProAVP

Description: Copeptin is a surrogate marker for arginine vasopression (AVP, anti-diuretic hormone, ADH) release. Copeptin and ADH are derived from the same pre-provasopressin precursor peptide. Unlike ADH, which is released in pulsatile patterns and rapidly removed from plasma, copeptin levels in plasma are relatively steady. Plasma copeptin specimens are very stable in comparison to ADH and are easy to measure by fluorescent immunoassay. Copeptin testing has now replaced ADH for the differential diagnosis of polyuria-polydipsia syndrome and distinguishes between central and nephrogenic diabetes insipidus (DI).

Patient preparation instructions: Discontinue diuretic or antidiuretic medications for at least 24 hours before test.
Collection Devices:
Red, Gold, or Lavender (EDTA) top tubes are also acceptable.
Specimen Required:
Plasma: 1.0 mL
Pediatric Plasma: 0.5 mL

Collect full tube to measure copeptin and osmolality on the same sample.
Store and ship frozen
Referral:

Adult Volume:  0.5 mL (two tubes)
Pediatric Volume: 0.3 mL (two tubes)
Shipping & Storage: Aliquot TWO tubes, store and send frozen to HSC or SBH.
 
IMPORTANT: For every specimen received, plasma must be aliquoted into TWO tubes and shipped frozen to SBH or HSC for referral.
One of the tubes is to be used for Osmolality measurements required for results reporting. Osmolality test (LIS code: OS) must be added and measured at SBH or HSC receiving site. Do not send aliquot to In-Common Labs unless Osmolality result is available in Delphic.
Referred Out Location: Specimen referred from HSC-MS5 or SBH to:
In-Common Laboratories
57 Gervais Drive
North York, Ontario
M3C 1Z2
Telephone: (416) 422-3000
Test ID: COPEPTIN
Testing location: London Health Sciences, London, ON
 
Requisition:
Reference Values:
Osmolality     
(mOsm/kg)		 Copeptin Reference Interval
(pmol/L)
270-280 ≤ 11.6
281-285 ≤ 13.7
286-290 1.5-15.3
291-295 2.3-24.5
296-300 2.4-28.2
Method of Analysis: Thermo Fisher Fluorescent Immunoassay
Availability:
Within 2 Weeks
See Also:
More Information:
Interpretation & Assay Interferences: From Timper K et al., J Clin Endocrinol Metab 2015; 100(6):2268-2274:
     - a baseline copeptin ≥21.4 pmol/L identified nephrogenic diabetes insipidus with 100% sensitivity and specificity
     - following a combined water deprivation/hypertonic saline infusion test, a copeptin level ≥4.9 pmol/L identified primary polydipsia and a copeptin level <4.9 pmol/L identified complete or partial central diabetes insipidus with 94-96% sensitivity and specificity
From Winzeler B et al., Lancet 2019; 394(10198):587-595:
     - at 60 min following an arginine stimulation test, a copeptin level ≥3.8 pmol/L identified primary polydipsia and a copeptin level <3.8 pmol/L identified complete or partial central diabetes insipidus with 93% sensitivity and specificity
 
PEDIATRIC:
Non-water-deprived pediatric subjects: copeptin reference interval
As suggested by a small study involving 15 children with polyuria and polydipsia from Tuli G et al., Clin Endocrinol (Oxf) 2018; 88(6):873-879:
- following a water deprivation test
     - copeptin >20 pmol/L: nephrogenic diabetes insipidus
     - copeptin 5-20 pmol/L: primary polydipsia
     - copeptin 2.2-4.9 pmol/L: diagnosis depends on plasma and urine osmolality
     - copeptin <2.2 pmol/L: complete central diabetes insipidus