An interventional study of Mannitol and Hypertonic Saline in Arginine Vasopressin Deficiency and Primary Polydipsia, sponsored by University Hospital, Basel, Switzerland. Recruiting at 1 site in Switzerland. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-06-18.
Sponsored by University Hospital, Basel, Switzerland · Not applicable, Interventional, and Diagnostic
The aim of this study is to evaluate whether a new test using mannitol infusion can diagnose the cause of polyuria-polydipsia syndrome as accurately as the current standard test (hypertonic saline infusion) and to compare which test patients prefer. The goal is to identify a simpler and more patient-friendly diagnostic approach.
Polyuria-polydipsia syndrome (PPS), characterized by excessive urination and fluid intake, can have different underlying causes, including a deficiency of the hormone vasopressin (AVP-D) or excessive fluid intake without AVP-D (primary polydipsia). Correctly identifying the cause is essential, as the treatments differ and an incorrect diagnosis can negatively impact patient care.
A blood marker called copeptin is used to support the diagnosis, as it reflects vasopressin levels in the body. Currently, the most accurate method involves measuring copeptin after stimulation with hypertonic saline. However, this test is complex, requires close medical monitoring, and can be uncomfortable for patients.
Mannitol is a substance already used in routine clinical care and may offer a simpler way to stimulate copeptin release. Early results suggest that it could provide similar diagnostic accuracy with fewer side effects and better patient comfort.
This study is a randomized, cross-over, multicenter trial in which participants undergo both tests (mannitol and hypertonic saline) in random order. The study compares the diagnostic accuracy and patient preference for both methods, as well as safety and tolerability. In addition, it explores whether other clinical and laboratory measures can further improve the diagnosis of PPS.
27 studies on the registry are indexed under Diabetes Insipidus, Neurogenic; 12 are open to participants now.
This study's planned enrollment of 144 is above the median of 42 across 23 interventional studies indexed under Diabetes Insipidus, Neurogenic.
Browse Diabetes Insipidus, Neurogenic studies →University Hospital, Basel, Switzerland is the lead sponsor of 990 studies on the registry; 189 are open to participants now.
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Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
GFR (glomerular filtration rate) is how much blood the kidneys filter each minute. It is usually estimated from a blood test — eGFR, by formulas such as CKD-EPI or MDRD — and some studies ask for it to be measured directly instead. Usually given in mL/min/1.73 m².
Check the method, the units and the minimum the study states. A value of 90 or above is in the normal-or-high range, but kidney damage can show in other tests too.
The New York Heart Association’s four classes of how much heart failure limits physical activity.
Studies set their own limit — many outside heart failure leave out class III–IV, while heart failure studies may ask for a particular class. Check the class this study names.
A score of how well the liver works in people with liver disease such as cirrhosis: class A is mild, B moderate and C severe.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
GFR and eGFR (kidney filtering)
GFR (glomerular filtration rate) is how much blood the kidneys filter each minute. It is usually estimated from a blood test — eGFR, by formulas such as CKD-EPI or MDRD — and some studies ask for it to be measured directly instead. Usually given in mL/min/1.73 m².
Check the method, the units and the minimum the study states. A value of 90 or above is in the normal-or-high range, but kidney damage can show in other tests too.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
NYHA class (heart failure)
The New York Heart Association’s four classes of how much heart failure limits physical activity.
Studies set their own limit — many outside heart failure leave out class III–IV, while heart failure studies may ask for a particular class. Check the class this study names.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Child-Pugh class
A score of how well the liver works in people with liver disease such as cirrhosis: class A is mild, B moderate and C severe.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Diagnostic evaluation of polyuria polydipsia syndrome through copeptin measurement after mannitol infusion.
Diagnostic Test: Mannitol
Diagnostic evaluation of polyuria polydipsia syndrome through copeptin measurement after HIS
Diagnostic Test: Hypertonic Saline
Intravenous infusion of 1.5g/kg body weight (max. 120g) mannitol is given over 30 minutes (≙ 7.5ml/kg body weight).
Intravenous infusion of NaCl 3% is given first as a bolus of 250ml over 15 minutes, then with an infusion rate of 0.15ml/kg body weight / minute (≙ 9ml/kg body weight/hour).
Overall Diagnostic Accuracy
The overall diagnostic accuracy is defined as the proportion of correct diagnoses out of all diagnoses based on the stimulated copeptin value. Final diagnosis will be made after termination of the study by two endocrine specialists who will be blinded to the copeptin results of the mannitol infusion.
Time frame: One time assessment at Follow up Visit 2 (10 weeks after baseline)
Patient Test Preference
Patient-reported preference between mannitol infusion and hypertonic saline infusion, assessed using a 5-point Likert scale ranging from -2 (strong preference for hypertonic saline) to +2 (strong preference for mannitol).
Time frame: 1 week after completion of both diagnostic tests
Diagnostic Performance Measures for AVP-D
Sensitivity, specificity, positive predictive value, and negative predictive value of mannitol infusion and hypertonic saline infusion for diagnosing AVP deficiency using predefined copeptin cut-offs.
Time frame: At completion of follow-up, 10 weeks after last diagnostic test
Diagnostic Performance Measures for PP
Sensitivity, specificity, positive predictive value, and negative predictive value of mannitol infusion and hypertonic saline infusion for diagnosing PP using predefined copeptin cut-offs.
Time frame: At completion of follow-up, 10 weeks after last diagnostic test
Optimal copeptin cut-off after mannitol infusion
Exploratory determination and validation of optimal copeptin cut-off values for differentiating AVP deficiency from primary polydipsia following mannitol stimulation.
Time frame: At completion of follow-up, 10 weeks after last diagnostic test
Frequency and severity of clinical symptoms
Frequency and severity of symptoms (e.g., thirst, headache, nausea, malaise) assessed using numeric rating scales during mannitol and hypertonic saline tests.
Time frame: During each test day (baseline to end of monitoring period 90 minutes/ 240 minutes)
Subjective burden of each test assessed by numeric rating scale
Patient-reported burden of each diagnostic test assessed using a numeric rating scale (NRS) (0-10).
Time frame: Immediately after each test day
Psychopathological assessment (STAI-T)
General anxiety levels is assessed by State-Trait Anxiety Inventory (STAI-T) questionnaire. The total trait score (STAI-T) ranges from 20 to 80, with higher scores indicating more pronounced anxiety.
Time frame: Baseline
Autistic traits
Autistic traits is assessed by Autism-Spectrum Quotient (AQ) questionnaire. The AQ consists of 50 items, with four choices for each item from "definitely agree" to "definitely disagree" and a total score from 0 to 50. A score above the proposed cut-off of 29 highlights significant traits of autism.
Time frame: Baseline
Quality of Life in Posterior Pituitary Disease
Currently, no disease-specific tool exists to assess treatment success for either desmopressin or oxytocin (OXT) therapy in patients with arginine vasopressin deficiency (AVP-D). To address this gap, we developed a novel multidimensional questionnaire in close collaboration with patients, patient representatives, and patient advocates. The PP-QoL consists of three parts: Part A assesses symptoms related to AVP-D (15 items), while Parts B (17 items) and C (21 items) focus on domains associated with OXT deficiency.
Time frame: Baseline and follow-up (10 weeks )
Change in oxytocin/neurophysin I levels
Change in circulating oxytocin and neurophysin I levels before and after each diagnostic test.
Time frame: Baseline and 90 minutes post-stimulation
Spearman's rank correlation coefficient between psychopathology questionnaires and oxytocin levels
Correlation between psychopathological questionnaires and oxytocin levels will be described using Spearman's rank correlation coefficient.
Time frame: Baseline and 90 minutes post-stimulation
Spearman's rank correlation coefficient between psychopathology questionnaire and neurophysin I levels
Correlation between psychopathological questionnaires and neurophysin I levels will be described using Spearman's rank correlation coefficient.
Time frame: Baseline and 90 minutes post-stimulation
Validation of clinical diagnostic score
Validation of a predefined diagnostic score using clinical and basal parameters
Time frame: After test day 2 and 10 weeks thereafter
Change of urinary copeptin levels
Change in urinary copeptin levels before and after mannitol and hypertonic saline stimulation.
Time frame: During test day 1 and test day 2 with a maximum of 3 month in between the two test days
Optimal urinary copeptin cut-offs
Exploratory determination of optimal urinary copeptin thresholds for differential diagnosis.
Time frame: 10 weeks after test day 2
Sex-specific copeptin response
Evaluation of sex-specific differences in stimulated copeptin levels and corresponding diagnostic cut-offs.
Time frame: During test day 1 and test day 2 with a maximum of 3 month in between the two test days and at study completion
Cost-efficiency of diagnostic tests
Exploratory assessment of healthcare costs associated with mannitol infusion versus hypertonic saline infusion.
Time frame: One time assessment at Follow up Visit 2 (10 weeks after baseline)
Started Jun 2026 (actual). Primary completion is estimated for Jun 2030, 48 months after the start.
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