The differential diagnosis of central diabetes insipidus (cDI) is difficult and the current test with the highest diagnostic accuracy is copeptin measurement after hypertonic saline infusion (HIS). Although the HIS improved diagnostic accuracy compared to the standard water deprivation test used for decades before, it still comprises great discomfort for patients due to the rise in serum sodium levels above 149mmol/l and requires the presence of medical staff at all times to guarantee safety of the test. The arginine stimulation test is routinely used to stimulate growth hormone. Own data in 52 patients with polyuria / polydipsia syndrome showed that arginine infusion is a potent stimulator of the neurohypophysis and provides a new diagnostic tool in the differential diagnosis of cDI. Copeptin measurements upon arginine stimulation (CAS) discriminated patients with diabetes insipidus vs. patients with primary polydipsia with a high diagnostic accuracy of 94%. To validate these results and to compare them against the HIS a large multicenter trial is needed, where the diagnostic accuracy of the CAS is compared to the HIS.
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The primary outcome is the overall diagnostic accuracy - defined as the proportion of correct diagnoses - of each diagnostic procedure in differentiating patients with central diabetes insipidus from patients with primary polydipsia.
Timeframe: 2 days