01 Aug Harmless or Hormone disorder? New Test Enables Quick Diagnosis For Drinking by the Liter
MedicalResearch.com Interview with:
Prof. Christ-Crain
Prof. Dr. Mirjam Christ-Crain
Professor of endocrinology, diabetes and metabolism
Heads the Department of Clinical Research
University and University Hospital of Basel
MedicalResearch.com: What is the background for this study? Would you briefly explain what is meant by Diabetes Insipidus?
Response: Drinking more than three litres per day with the equivalent increase in urination is regarded as too much. This drinking by the liter – known as “polyuria polydipsia syndrome” – usually develops over time through habit, or can be a side effect of a mental illness.
In rare cases, however, it may be caused by diabetes insipidus. This is when the pituitary gland lacks the hormone vasopressin, which regulates the water and salt content in our body. Patients have a decreased ability to concentrate the urine, therefore lose a lot of fluid and have to increase their fluid intake accordingly to prevent dehydration (= Diabetes insipidus).
The distinction between what is considered a “harmless” primary polydipsia and a diabetes insipidus is crucial, as their therapy is fundamentally different. Diabetes insipidus must be treated with the hormone vasopressin, while patients with primary polydipsia require behavioural therapy to reduce their habitual drinking. A wrong therapy can have life-threatening consequences as treatment with vasopressin without indication can lead to water intoxication.
MedicalResearch.com: What are the main findings?
Response: Previously, the differentiation between these two conditions was made using a “water deprivation test” in which the patient was not allowed to drink any liquid for 16 hours after which the doctors would interprete the concentration of the urine. However, this test was often misleading and only led in about half of all cases to a correct diagnosis. Furthermore, a 16-hour water deprivation test is extremely unpleasant and stressful for the patients.
A study involving around 150 patients in 11 clinics compared the conventional “water deprivation test” with a new diagnostic method. It consists of a 2-hour infusion with a hypertonic saline solution; after that, the concentration of the biomarker copeptin, which reflects the content of the hormone vasopressin in the blood, is measured in the patients’ blood.
This method has a much higher diagnostic accuracy: 97 percent of all patients were correctly diagnosed and treated quickly. The new test is now available for clinical use.
MedicalResearch.com: What should readers take away from your report?
Response: Readers should know that there is a new and more reliable test for the differentiation of these two disorders. As the editorial in the NEJM states, the new test will probably replace the cumbersome water deprivation test in the future.
MedicalResearch.com: What recommendations do you have for future research as a result of this work?
Response: The saline infusion test is associated with more side effects (even if they were only mild) and higher sodium levels than the water deprivation test. It needs constant supervision by a physician. If there is another, even simpler, stimulus for copeptin, without these risks, and which could be done outside a hospital setting, this would be advantageous for patients and physicians alike. We are working on this topic and trials are already ongoing.
MedicalResearch.com: Is there anything else you would like to add?
Response: Copeptin measurement was paid by Thermofisher, the manufacturer of the Copeptin assay.
Drinking excessive amounts of fluids can be a medically unremarkable habit, but it could also signify a rare hormone disorder. A new procedure now enables a fast and reliable diagnosis. Researchers from the University of Basel and University Hospital Basel reported these findings in the New England Journal of Medicine.
Citation:
A Copeptin-Based Approach in the Diagnosis of Diabetes Insipidus
Wiebke Fenske, M.D., Ph.D., Julie Refardt, M.D., Irina Chifu, M.D.,Ingeborg Schnyder, M.D., Bettina Winzeler, M.D., Juliana Drummond, M.D., Antônio Ribeiro-Oliveira, Jr., M.D., Ph.D., Tilman Drescher, M.D., Stefan Bilz, M.D., Deborah R. Vogt, Ph.D., Uwe Malzahn, Ph.D., Matthias Kroiss, M.D., Ph.D., August 2, 2018
N Engl J Med 2018; 379:428-439
DOI: 10.1056/NEJMoa1803760
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Last Updated on August 1, 2018 by Marie Benz MD FAAD