New test rapidly diagnoses disorder linked to excessive fluid intake

Aug. 2 (UPI) -- Researchers have developed a new procedure that quickly diagnoses a rare hormone disorder associated with drinking excessive amount of fluids.

The new test uses a two-hour infusion of hypertonic saline solution, as compared to a water deprivation test that only provided a diagnosis in half the cases. Researchers at the University of Basel and University Hospital Basel in Switzerland published their findings Thursday in The New England Journal of Medicine.

Drinking more than 100 ounces of liquid a day, with the equivalent increase in urination, is regarded as excessive, according to a press release.

This "polyuria-polydipsia syndrome" can be a side effect of a mental illness, but in rare cases it may be caused by diabetes insipidus.

In this disorder, the pituitary gland lacks the hormone vasopressin, which regulates the body's water and salt content. Patients lose a lot of fluid with excessive urination and increase their fluid intake correspondingly to prevent dehydration.

Medical personnel have distinguished between "harmless" primary polydipsia and diabetes insipidus.

Diabetes insipidus is treated with the hormone vasopressin and patients with primary polydipsia require behavioral therapy to cut down on the habit.

If vasopressin is used incorrectly, it can lead to water intoxication.

In a water deprivation test, participants couldn't drink any liquid for 16 hours and then doctors would analyze their urine. Besides being misleading, the test is extremely unpleasant and stressful for the patients, according to researchers.

For the study, 156 patients in 11 clinics with hypotonic polyuria underwent water-deprivation and hypertonic saline infusion tests between 2013 and 2017.

After the hypertonic saline solution, the concentration of the biomarker copeptin, which reflects the content of the hormone vasopressin in the blood, is measured.

Ninety-five percent of all patients were correctly diagnosed in the new test compared with the traditional method of 73 percent.

Primary polydipsia was determined in 57 percent of the patients, central diabetes insipidus in 41 percent and nephrogenic diabetes insipidus in 2 percent.