Session: SUN 130-162-Neuroendocrinology
Poster Board SUN-161
Background: In polyuria-polydipsia syndrome, primary polydipsia must be distinguished from central and nephrogenic diabetes insipidus (DI). A correct discrimination is mandatory since inadequate treatment may lead to serious complications. The diagnostic gold standard is the water deprivation test with direct or indirect measurement of arginine vasopressin (AVP). However, test interpretation is problematic, and direct measurement of AVP is hampered by methodological difficulties. The aim of this study was to evaluate the diagnostic accuracy of copeptin in the differential diagnosis of DI.
Design:Prospective multicenter study in four tertiary referral centers in Switzerland and Germany.
Methods: The ‘CoSIP-Study’ included consecutive patients >18 years with a history of polyuria in the presence of polydipsia. All participants underwent a water deprivation test. The test started at 8 am without prior fluid restriction with a baseline blood and urine sampling and was terminated as soon as serum sodium levels increased >147mmol/L. If this cutoff was not reached by fluid deprivation alone a 3% saline infusion was administered. At baseline and hourly during the water deprivation test, a serum sample was obtained for measurement of copeptin and AVP.
Results:We present results of the first 52 patients with full data available (complete central DI 13 patients, partial central DI 12 patients, primary polydipsia 17 patients, nephrogenic DI 10 patients). 29 were women, 23 were men. Mean (± SD) age was 45 ± 15.7 years. Baseline copeptin levels ranged from 21.4-117 pmol/L in patients with nephrogenic DI, from 0.7-5.1 pmol/L in patients with central DI (complete: 0.7-4.1 pmol/L; partial: 0.8-5.1 pmol/L) and from 0.9-13.5 pmol/L in patients with primary polydipsia. Without prior thirsting, a single baseline copeptin level of >20 pmol/L perfectly differentiated nephrogenic DI from all other etiologies with a sensitivity and specificity of 100%, rendering a water deprivation test unnecessary. Furthermore, a delta copeptin (difference between baseline copeptin and copeptin upon osmotic stimulation, i.e. at a plasma sodium level >147 mmol/L) <2 pmol/L differentiated patients with central DI from patients with primary polydipsia with a specificity of 95.8%, a sensitivity of 94.1% and a positive likelihood ratio of 22.6.
Conclusion: Copeptin is a promising new tool in the complex diagnosis of polyuria-polydipsia syndrome.
Nothing to Disclose: KT, MK, WKF, FK, BA, NF, JR, PK, BA, CS, BM, MC
*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm
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