Use of the arginine-stimulated copeptin test in polyuric syndrome in paediatrics. Experience in three patients

Llorens Núria González; Carranza Elsa Puerto; Viñals Eduard Mogas; Martorell Ariadna Campos; Fernández Diego Yeste; León María Clemente

Introduction: Differential diagnosis of partial arginine vasopressin deficiency (P-AVPD) and primary polydipsia (PP) can be challenging. Arginine-stimulated copeptin concentrations have been used to differentiate between arginine vasopressin deficiency (AVPD) and PP, setting a copeptin value of 3.8pmol/L at 60 min as a cut-off point in adults.

Objective: To evaluate the efficacy and safety of the arginine-stimulated test in paediatrics.

Methods: Descriptive and prospective study on a diagnostic method in six paediatric patients with polydipsia-polyuria syndrome (PPS).

Inclusion criteria: Patients under 18 years with polyuria (>2mL/kg/h), normal glycaemia and no electrolytic changes. The arginine-copeptin test is performed with analytical control and vital signs (Times: basal, 0', 30', 60', 90', 120'). Patients description and results (Table 1 and 2): -Patient 1: 5-year-old boy with sudden PPS and MRI showing hypoplastic adenohypophysis and absence of neurohypophysis signal. Arginine-copeptin test <3.8pmol/L. -Patient 2: 12-year-old boy with long-standing PPS and syntelencephaly without alterations in the hypothalamic-pituitary region. Arginine-copeptin test >3.8pmol/L. -Patient 3: 13-year-old boy with sudden PPS. MRI showed an absence of the neurohypophysis and thickening of the pituitary stalk, etiological study pending. Arginine-copeptin test <3.8pmol/L. -Patient 4: 3-year-old girl with SGA, monosomy X, and Kabuki-like syndrome with long-standing PPS. MRI without alterations in the hypothalamic-pituitary axis. Arginine-copeptin test >3.8pmol/L. -Patient 5: 4-year-old girl with long-standing PPS. Arginine-copeptin test >3.8pmol/L. -Patient 6: 10-year-old boy with GH deficiency under treatment and MRI showing interruption of the pituitary stalk and ectopic neurohypophysis. He presents long-standing PPS. Arginine-copeptin test >3.8pmol/L. All patients were asymptomatic and hemodynamically stable during the procedure. Blood tests at the beginning and end of the test show no alterations.

Table 1: Water-restriction test
	1	2	3	4
Duration (hours)	15	17	Basal (without restriction; plasma osmolality of 303mOsm/Kg)	10
Urinary osmolarity before Desmopressin (mOsm/kg)	601	495	98	304
Urinary osmolarity after Desmopressin (mOsm/kg)	845	687	507	415

Table 2: Arginine-copeptin test
1	2	3	4	5	6
	Copeptin (pmol/L)
Basal	2,4	3,8	1,61	4.42	2.7	3,94
30’	2,5	4	1,48	5.24	3	5,3
60’	2,3	4,13	1,78	8.44	4.8	5,2
90’	1,8	3,8	1,98	4.5	6
120’	2,4		1,47	9.72	3.7	5,8
180’					3.7	4,5
Diagnosis	P-AVPD	PP	AVPD	PP	PP	PP

Conclusion: The arginine-stimulated copeptin test is a safe procedure and can represent an alternative to the diagnosis of AVPD.

ESPE Abstracts

P2-27