Indexed on: 15 Aug '18Published on: 15 Aug '18Published in: Endocrine practice : official journal of the American College of Endocrinology and the American Association of Clinical Endocrinologists
The water deprivation test (WDT) is widely used for the differential diagnosis of the polyuria-polydipsia syndrome (PPS). However, it is inconvenient and may not always be precise in differentiating partial forms of diabetes insipidus (DI) from primary polydipsia (PP). The aim of this study was to evaluate the results of a combined outpatient and inpatient overnight WDT protocol that included an overnight non-supervised period concerning its feasibility and safety. Retrospective analysis of clinical data and laboratory results of 52 patients with PPS undergoing WDT in a single center was undertaken. PP was the most frequent diagnosis, followed by complete central DI (CDI), partial CDI and nephrogenic DI (NDI). Over 90% of the patients showed an expected increase in serum osmolality at the end of the dehydration period. There were no reports of complications during the overnight deprivation period. Post-dehydration urine osmolality and urine-to-serum osmolality ratio significantly differentiated all the groups (p< 0.05), except for CDI and NDI, which could be differentiated by basal and post-dehydration vasopressin (AVP) levels (p<0.05 for both). Although these measurements were able to differentiate patients according to their allocation groups, results from WDT and direct AVP levels may often ask for a comprehensive diagnostic approach, particularly in the challenging groups of PP and partial CDI. A combined outpatient and inpatient overnight WDT protocol is safe and feasible when the test is performed with special care at experienced centers. Newer diagnostic tools are expected to improve the accuracy of PPS diagnosis. AQP2 = Aquaporin-2; AVP = Vasopressin; AVPR2 = AVP receptor subtype 2; CDI = Central Diabetes Insipidus; DDAVP = Desmopressin; DI = Diabetes Insipidus; IQR = Interquartile range; MRI = Magnetic Resonance Imaging; NDI = Nephrogenic Diabetes Insipidus; PP = Primary Polydipsia; PPS = Polyuria-polydipsia Syndrome; RIA = Radioimmunoassay; S_osm = Serum osmolality; USA = United Sates of America; U_osm = Urine osmolality; WDT = Water Deprivation Test; WHO = World Health Organization.