In the investigation of diabetes insipidus (DI) and primary polydipsia (PP) in patients with confirmed polyuria (>40 mL/kg/d)*: - A baseline copeptin level >21.4 pmol/L is 100% sensitive and specific for nephrogenic diabetes insipidus - A baseline Copeptin level < 2.6 pmol/L with prior fluid deprevation (> 8hrs) will indicate complete central DI(5) - A stimulated copeptin** > 4.9 pmol/L PP likely and <4.9 pmol/L partial central DI likely (94.0 % specificity and 94.4% sensitivity). [Note: * Without concurrent diabetes mellitus, hypercalcemia, pregnancy, uncorrected thyroid or adrenal insufficiency, and heart failure; ** At sodium levels >147 mmol/L following water deprivation]
5 mL SST gel, lithium heparin, EDTA or citrate are acceptable.
Central Sydney Container:
Min. Specimen Amount
Spin blood and send serum/plasma frozen.
Plasma EDTA and citrate samples are stable at room temperature for 7 days and 14 days at 4°C. Serum and plasma lithium heparin show <20% loss of recovery from 7 days at room temp. Samples stored at room temp for more than 7 days are not acceptable.
Interpret results with simultaneous plasma & urine osmolality.
Assayed on Monday, Wednesday and Friday.
BRAHMS Thermofisher Kryptor Compact Plus
Brief Clinical Notes:
Copeptin is used in the diagnosis of central and nephrogenic diabetes insipidus.
(1) The Reference Interval for Non water Deprived and Non Fasting Adults was determined from an in-house RPAH Endocrinology Laboratory Study. (2) Keller T, Tzikas S, Zeller T, et al: Copeptin improves early diagnosis of acute myocardial infraction. J A, Col Cardiol 2010 , 1;55(19): 2096-2106. (3) Reference Interval for fasting and water deprived adults ( > 8hours) was adopted from the Mayo Clinic in house study, www. Mayoliniclabs.com. (4) Du JM, Sang G, Jiang CM, et al, Relationship between plasma copeptin levels and complications of community acquired pneumonia in preschool children. Peptides 2013Jul, 45: 61-65. (5) Fenske W, Quinkler M , et al, Copeptin in the Differential Diagnosis of the Polydipsia-Polyuria Syndrome- Revisiting the Direct and Indirect Water Deprivation Tests, J Clin ENdocrinol Metab 96: 1506-2011.
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Royal Prince Alfred Hospital - NSW
Results Ph: (02) 9515 8022
Scientist Ph: (02) 9515 6352
Fax: (02) 9515 7640