ESPE Abstracts

Background: Polyuria-polydipsia syndrome (PPS) is a common condition in children, and its etiology is not always easily elucidated. Although the water deprivation test remains the gold standard for diagnosis, its limitations necessitate the search for alternative diagnostic methods. Due to its stability, copeptin is a valuable current parameter that is considered more reliable than AVP measurement. This study aims to compare copeptin levels between patients with central diabetes insipidus (CDI) and healthy control groups and to establish a copeptin threshold in clinically, laboratory, imaging-confirmed, and long-term monitored cases of CDI.

Methods: The study included patients diagnosed with CDI who were followed up between 2005 and 2023 and a healthy control group. During routine check-ups between August 1, 2023, and December 1, 2023, blood samples were collected before the morning dose of desmopressin to measure copeptin levels. The control group consisted of children who visited the pediatric clinics during the same period. The copeptin levels of patients and the control group were compared.

Results: The study included 81 participants:22(27.2%) patients and 59(72.8%)controls. The mean decimal ages of the patient and control groups were 11.79±4.33 and 11.48±5.05, respectively. In the patient group, 86.4% had operated intracranial masses,9.1% had familial diabetes insipidus, and 4.5% had DIDMOAD syndrome, with 77.3% having undergone surgery. The mean sodium level at diagnosis was 151.95±9.34 mmol/l, mean blood osmolality was 307.41±16.69 mOsm/kg, and mean urine osmolality was 141.86±73.19 mOsm/kg. The mean copeptin levels in the patient and control groups were 3.56±1.34 pmol/l and 9.30±2.70pmol/l, respectively, showing a statistically significant difference between the two groups(P <0.001). A ROC curve was plotted to determine a cutoff value for diagnosis, with an area under the curve value of 94.6%. The cutoff point was established at 5.75pmol/l, with a 95% confidence interval of 89.2% to 99.9%. The sensitivity was 95%, and the specificity was 88%, indicating a significant difference between the groups(P <0.001). No significant difference in copeptin levels was found in the patient group regarding gender and obesity status(P = 0.824; P = 0.700), while a significant difference was observed concerning pubertal status(P = 0.039). No significant difference in copeptin levels was found in the control group regarding gender, obesity status, and pubertal stage(P = 0.865; P = 0.256; P = 0.943).

Conclusion: Determining copeptin levels is reliable in the differential diagnosis of PPS in children. However, studies with larger sample sizes are needed to establish more precise threshold values for clinical application.