Prospective evaluation of the novel biomarker copeptin in the differential diagnosis of diabetes insipidus against the standard diagnostic test methods.
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).
Study Type
OBSERVATIONAL
Enrollment
156
Classical water deprivation test alone
classical water deprivation test plus plasma copeptin cut-off levels
hypertonic saline infusion test plus plasma copeptin measurement
Univerisity Hospital Basel
Basel, Canton of Basel-City, Switzerland
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
Time frame: beginning and end of protocol, up to 9hours
Sensitivity, specificity, positive and negative predictive value
each diagnostic test
Time frame: 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
Time frame: 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
Time frame: 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
Time frame: 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
Time frame: before or after tests
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