Introduction: Copeptin is a stable AVP surrogate, secreted in equimolar relationship, who has been proposed for the diagnosis of AVP-related hypo and hypernatremic disorders, i.e. the syndrome of inappropriate ADH secretions (SIADH), the cerebral/renal salt wasting syndrome (C/RSW) and diabetes insipidus (DI). Few data exist about the normal ranges for plasma copeptin levels in the pediatric age, reported between 2.4-8.6 pmol/L. The aim of this study is to represent the plasma copeptin distribution in a large pediatric cohort.
Methods: Plasma copeptin levels have been measured in 128 children and adolescents referred for other diseases than AVP-related disorders to the Department of Pediatric Endocrinology of Regina Margherita Children's Hospital in Turin in the period July 2016-May 2018. Plasma sample for copeptin analysis was collected early in the morning and the cohort was then splitted on the basis of recorded ingested fluid in the 6-8h before the sampling: Group A, with fluid fasting, Group B with free access to fluids.
Results: In the studied cohort plasma sodium level was 141.3 ± 1.63 in Group A (n=40) whereas in Group B (n=80) was 140.5 ± 1.81 (P=0.02). Significant difference was observed between the two groups also for plasma osmolality (285.6 ± 5.89 vs 283.5 ± 2.99 respectively, P=0.008). Mean plasma copeptin level was 6.76 ± 3,18 pmol/ (range 2-14.9 pmol/L). No difference was present among boys (n=42) and girls (n=86), displaying 6.96 ± 0.5 and 6.65 ± 0.34 values, respectively (P=0.61). Plasma copeptin levels in Group A were 10.26 ± 0.43 pmol/l, in Group B 5.16 ± 0.18 pmol/L (P<0.001). In all distribution percentiles copeptin levels were higher in children and adolescents with nocturnal liquid fasting (3th percentile 3.42 vs 2.47 pmol/L; 5th percentile 3.9 vs 2.6 pmol/L; 10th percentile 5.94 vs 2.8 pmol/L; 25th percentile 8.73 vs 4 pmol/L; 50th percentile 10.6 vs 4.9 pmol/L; 75th percentile 12.3 vs 6.18 pmol/L; 90th percentile 13.84 vs 7.6 pmol/L; 95th percentile 14.3 vs 8.24 pmol/L; 97th percentile 14.76 vs 9.76 pmol/L).
Conclusion: Since plasma copeptin represents an emerging tool to investigate sodium and osmolality derangements, its evaluation should be included in the diagnostic flow-chart of AVP-related disorders. However, due to the extreme sensitivity of this parameter, in the interpretation of its levels, oral or intravenous administered fluids should be accurately considered.
19 - 21 Sep 2019
European Society for Paediatric Endocrinology