ESPE Abstracts

Introduction: Diagnosis of central diabetes insipidus (CDI) remains challenging. Water deprivation test and hypertonic saline infusion, as established diagnostic tests, are mentally and physically demanding for patients. Copeptin response to arginine-stimulation and insulin tolerance test (ITT) has been shown to be a putative parameter in the diagnosis of CDI in adults, but data are lacking for children and adolescents.

Methods: In this single-centre retrospective study, we identified paediatric patients with suspected pituitary disorders who underwent standard arginine-testing or ITT. Patients with CDI, matched controls without CDI and primary polydipsia (PP) were identified. Diagnoses were confirmed retrospectively using comprehensive clinical and diagnostic characteristics. Serum copeptin concentrations were measured using a commercially available automated immunofluorescence assay (B.R.A.H.M.S Copeptin¬proAVP KRYPTOR®) in samples stored for a median of 4.0 years (1.3-10.8) and collected before and 60 minutes after arginine-infusion or subsequently in ITT. Cut-off analyses were performed using ROC curves.

Results: Serum samples from 32 patients with CDI, 32 matched controls and 5 patients with PP (n=69; 51 males, 18 females) and arginine test were available for analysis. Median copeptin concentrations increased from 4.47 pmol/l (IQR: 3.47-8.36) to 6.96 pmol/l (IQR: 4.51-12.89; P<0.001) in controls, from 1.46 pmol/l (IQR: 1.21-2.12) to 1.44 (IQR: 1.10-1.87; P=0.645, ns) in CDI and from 4.40 pmol/l (3.95-6.33) to 9.58 pmol/l (8.19-11.42; P<0.001) in PP. The published cut-off value of 3.8 pmol/l revealed a sensitivity of 100 % and a specificity of 86.5 % in confirming CDI. So far copeptin was measured in 7 patients with CDI and 3 controls at 0 and 60 minutes of ITT revealing a change from 1.48 pmol/l (IQR: 1.18-1.95) to 1.90 pmol/l (IQR: 1.43-4.12, P= 0.593, ns) and 4.87 pmol/l to 11.20 pmol/l (P=1.000), respectively.

Conclusion: Our results suggest that arginine-stimulated serum copeptin concentrations are a sensitive and specific diagnostic tool for CDI in paediatric patients, which may replace and simplify the conventional diagnostic pathway of water deprivation testing and hypertonic saline infusion. The copeptin response to ITT needs further evaluation.