Endocrine Abstracts

Aim: To assess the diagnostic value of a 3% hypertonic saline infusion test in comparison with a set of clinical and laboratory data (including a water deprivation test and MRI data) for the purpose of differential diagnosis between ADH deficiency and primary polydipsia (PP).

Materials and Methods: An interventional comparative study included 90 patients with confirmed polyuria-polydipsia syndrome. In order to assess the diagnostic characteristics, all subjects underwent sequential tests with osmotic stimulation: a 3% hypertonic saline infusion test and a water deprivation test.

Results: The study analyzed data from 90 patients who had underwent both osmotic stimulation tests. Based on the results of an analysis of the clinical, anamnestic, laboratory and instrumental data (MRI) and the results of a water deprivation test, a final diagnosis of ADH deficiency was made in 48 (53%) patients and 42 (47%) patients were diagnosed with PP. A diagnostic accuracy of the 3% hypertonic saline infusion test were calculated: sensitivity 98% (95% CI: 89%; 100%); specificity 98% (95% CI: 87%; 100%. Adverse events were studied: chills occurred significantly more often (31% vs 12%, P<0.003) during the 3% hypertonic saline infusion test, other signs of dehydration (dizziness, fog before the eyes, headache), and an increase in Na level >155 mmol/l were observed at equally frequency during both tests. The duration of the water deprivation test was 7 times higher than that of the 3% hypertonic saline infusion test (11 [11; 16] hours vs 1,5 [2; 2,5], р <0.001).

Conclusion: The 3% hypertonic saline infusion test has a high overall diagnostic accuracy (98%; 95% CI 92% to 100%) if compared to the set of clinical, laboratory and instrumental data of patients (including a water deprivation test). The advantage of the 3% hypertonic saline infusion test is its short duration and, as a consequence, better tolerability and compliance, while no significant differences in the occurrence of adverse events during the tests were noted.