Copeptin assays in children for the differential diagnosis of polyuria-polydipsia syndrome and reference levels in hospitalized children.

OBJECTIVES: Polyuria-polydipsia syndrome (PPS) is a common presentation in children but the differential diagnosis rests on burdensome water deprivation tests. The aims of this study were to determine a copeptin threshold to distinguish patients with central diabetes insipidus from those with primary polydipsia and to estimate the normal range of copeptin concentrations in children. DESIGN: Single-centre retrospective descriptive study. PATIENTS: Two hundred and seventy-eight children aged 2 months to 18 years who consulted for PPS (N = 40) or other reasons (control group, N = 238) at La Timone University Hospital in Marseille, France, between April 2015 and September 2019 and had a copeptin assay. MEASUREMENTS: Ultrasensitive copeptin assays on blood samples. RESULTS: Among the children with PPS, the mean copeptin concentrations were 1.72, 55.2 and 15.7 pmol/l in those with central diabetes insipidus (N = 21), nephrogenic diabetes insipidus (N = 3), and primary polydipsia (N = 16), respectively. Copeptin levels lower than 3.53 pmol/l were diagnostic of central diabetes insipidus with 100% sensitivity and 87.4% specificity (p < .001). The 5th-95th copeptin percentile range in the control group was 2.53-21.03 pmol/L. Copeptin levels were significantly higher in boys than in girls but there was no association with age, pubertal stage, body mass index, or the reason for consulting. CONCLUSIONS: Our results indicate copeptin assays may be valuable in the differential diagnosis of PPS in children. Larger prospective studies are required to establish their accuracy in everyday clinical practice.

The interplay between bone and vessels in pediatric CKD: lessons from a single-center study.

OBJECTIVE: Mineral and bone disorders associated to chronic kidney disease (CKD-MBD) are a daily challenge for pediatric nephrologists, with a significant risk of long-term bone and vascular comorbidities. METHODS: This single-center study is a prospective transversal evaluation of pediatric CKD patients of our center, part of the European 4C study. In addition to clinical and biochemical data, vascular and bone evaluation was performed: 24-h blood pressure assessment, carotid intima-media thickness (cIMT), pulse wave velocity (PWV), and high-resolution peripheral quantitative computed tomography (HR-pQCT) at the ultra-distal tibia. Results are presented as median (range). RESULTS: At a median age of 12.9 years (10.2-17.9), SDS height of - 1.0 (- 3.3-1.2) and estimated glomerular filtration rate (eGFR) of 33 mL/min/1.73m2 (11-72), 32 patients (8 girls) were evaluated. Median calcium, phosphate, parathyroid hormone (PTH), and 25 OHD3 levels were 2.44 mmol/L (2.24-2.78), 1.43 mmol/L (1.0-2.7), 80 pg/mL (9-359), and 70 nmol/L (32-116), respectively. Bivariate Spearman and backward multivariable analyses showed that calcium and bone trabecular thickness (Tb.Th), were positively associated with diastolic and mean arterial blood pressure (both for the 24 h, day and night assessment), whereas PTH and vitamin D did not predict blood pressure. CONCLUSIONS: We show that the greater the serum levels of calcium, the greater the (diastolic and mean) blood pressure; moreover, the greater the Tb. Th, the greater the (diastolic and mean) blood pressure. The role of calcium supplements to explain such findings in early pediatric CKD can be discussed.