Use of Copeptin in Diabetes Insipidus

Study Overview
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Brief Summary
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Prospective evaluation of the novel biomarker copeptin in the differential diagnosis of diabetes insipidus against the standard diagnostic test methods.

Detailed Description
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Purpose of this study is to compare the overall diagnostic accuracy of the three following diagnostic test procedures in diabetes insipidus (central, nephrogenic) and primary polydipsia: a) classical water deprivation test alone, b) classical water deprivation test plus plasma copeptin cut-off levels, c) hypertonic saline infusion test plus plasma copeptin measurement. The investigators hypothesize that firstly b) and c) is better as a). Secondly the investigators hypothesize that c) is non-inferior to b).

Official Title
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Use of Copeptin in the Differential Diagnosis of Diabetes insipidus-a Prospective International Study

Conditions
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Diabetes Insipidus, Primary Polydipsia

Intervention / Treatment
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* Other: Water deprivation test
* Other: Water deprivation test
* Other: Hypertonic saline infusion


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Polyuria or/and Polydipsia or/and therapy with synthetic adenovirus proteinase (AVP) derivate Urine osmolality <800mOsm/kgH20 Exclusion Criteria: Polyuria due to diabetes mellitus Hypokalemia Hyperkalemia (>5mmol/l) Hypercalcemia Kidney disease (min.: glomerular filtration rate (GFR) 60ml/min/1.73m2) Pregnancy Hyponatremia >135mmol/L Hypernatremia >145mmol/L Hypo- or hypervolemia uncorrected adrenal or thyroidal deficiency Cardia failure Epilepsia Uncontrolled hypertension

Ages Eligible for Study
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Minimum Age: 16 Years
Maximum Age: 80 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Intervention/Treatment |
| --- |
|Other: Water deprivation test|Classical water deprivation test alone|
|Other: Water deprivation test|classical water deprivation test plus plasma copeptin cut-off levels|
|Other: Hypertonic saline infusion|hypertonic saline infusion test plus plasma copeptin measurement|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Overall diagnostic accuracy | Ratio of the number of correctly diagnosed patients to the number of all tested patients for the tests: classical water deprivation test alone classical water deprivation test plus plasma copeptin cut-off levels hypertonic saline Infusion test plus plasma copeptin measurements | beginning and end of protocol, up to 9hours | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Sensitivity, specificity, positive and negative predictive value | each diagnostic test | beginning and end of protocol, up to 9hours | 
| post-hoc best copeptin cut-off optimising overall performance | best copeptin cut-offs for differentiation between different diagnosis of polyuria-polydipsia syndrome | beginning and end of protocol, up to 9hours | 
| subjective burden as rated by patients on visual analogue scale | water deprivation test and hypertonic saline Infusion test | beginning, during and end of protocol, up to 9hours | 
| Predictive value of specific anamnestic and clinical features | Evaluation of anamnestic and clinical features to test-independently predict final diagnosis of polyuria-polydipsia syndrome | before tests | 
| Predictive value of absent bright spot in posterior pituitary enlargement | Evaluation of predictive value of absent bright spot in T1 weighted cranial MRI scans | before or after tests | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Copeptin, differential diagnosis of polyuria polydipsia syndrome, diabetes insipidus, compulsive water drinking, water deprivation test, Diabetes insipidus (central and nephrogenic)