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.
Who can participate
Age range
18 Years – 95 Years
Sex
ALL
See this in plain English?
AI-rewrites the medical criteria so a patient or caregiver can understand them. Always confirm with the trial site.
Inclusion Criteria:
* Age ≥ 18 years
* Hypotonic polyuria / polydipsia syndrome defined as: polyuria \>50ml/kg body weight/24h and polydipsia \>3l /24h or known diabetes insipidus under treatment with DDAVP
* Urine-Osmolality \<800mOsm/L
Exclusion Criteria:
* Polyuria / polydipsia secondary to diabetes mellitus, hypercalcemia or hypokalemia
* Nephrogenic diabetes insipidus (defined as baseline copeptin level \>21.4pmol/L)
* Evidence of any acute illness
* Epilepsy requiring treatment
* Uncontrolled arterial hypertension (blood pressure \>160/100mmHg at baseline)
* Cardiac failure (NYHA III-IV)
* Liver cirrhosis (Child B-C)
* Uncorrected adrenal or thyroidal deficiency
* Patients refusing or unable to give written informed consent
* Pregnancy or breast feeding
* End of life care
Questions worth asking your doctor
Bring these to your next appointment. They're a starting point for a shared conversation — not a sign you qualify or a recommendation to enrol.
1Based on my diagnosis and history, is this trial worth exploring for me — or is there a standard treatment we should try first?
2What does this trial's phase tell us about how much is already known about its safety and benefit?
3What would taking part actually involve for me — visits, tests, time, and travel?
4What are the known and possible risks or side effects I should weigh, and how would they be monitored?
5If this trial isn't the right fit, what other options or trials would you suggest I look into?
Generated to help you prepare — always confirm anything about your own eligibility and care with the study team and your doctor.
Questions for the trial coordinator
The trial coordinator is the person who runs the study day to day. These cover the practical side — logistics, costs, and what taking part would actually mean for your life. The study team confirms whether you meet the criteria; these are questions to ask, not a sign you qualify.
1What does taking part actually involve week to week — how many visits, where, and how long does each one take?
2What costs are covered by the study, and what might I have to pay for myself, including travel, parking, or time off work?
3What happens during screening, and what happens if the study team confirms I don't meet the criteria after those tests?
4Who pays for the scans, blood work, and other tests the trial requires — the study, my insurance, or me?
5How will being in the trial affect my regular care, and will my own doctor stay informed and involved?
6Can I leave the trial at any point if I change my mind, and what would happen to my care if I do?
A starting point for the conversation — always confirm anything about your own eligibility, costs, and care with the study team and your doctor.
What they're measuring
1
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.