Is copeptin a reliable biomarker of primary monosymptomatic nocturnal enuresis?

Introduction
The position of copeptin (C-terminal fragment of antidiuretin propeptide) as a marker of primary monosymptomatic nocturnal enuresis (PMNE) is under debate, and there are no data on the relation between copeptin and clinical and biochemical parameters in these patients. Aim of the study was to assess the level of serum copeptin in children with PMNE and to look for a relation between copeptin and selected clinical and biochemical parameters in these children.

Material and methods
Twenty-five children recruited for the trial fulfilled the following criteria: clinical diagnosis of PMNE, age 5-15 years, normal creatinine level, normal ultrasonographic image of kidneys and urinary tract. The following parameters were evaluated: serum copeptin, creatinine, sodium, potassium, hematocrit and urine specific gravity. Twenty healthy children were included in the control group.

Results
Children from study and control groups did not differ in serum copeptin, sex, age creati­nine, sodium, hematocrit and specific gravity. Serum potassium level remained normal in subjects but was significantly higher in the study group. In children with PMNE we found no relation between serum copeptin level and sex, kidney function, sodium, and urinary specific gravity. We found a negative correlation between copeptin and bladder capacity and trends towards positive relations between copeptin and age, as well as hemoglobin. In the subgroup of children with normal bladder capacity a trend towards a positive correlation between copeptin and potassium was found.

Conclusions
Copeptin may be a marker of hydration status in children with PMNE. The relation between potassium and copeptin levels and the clinical significance of the relation require further studies.