Evaluation of Urinary Aquaporin 2 and Plasma Copeptin as Biomarkers of Effectiveness of Desmopressin Acetate for the Treatment of Monosymptomatic Nocturnal Enuresis

Purpose: Desmopressin is a synthetic V2 specific analogue of antidiuretic hormone (arginine vasopressin) that is widely used as first line treatment for monosymptomatic nocturnal enuresis. However, no biomarkers to predict desmopressin effectiveness have yet been established. Because arginine vasopressin is unstable, we prospectively measured the major urine concentration factor aquaporin 2 and serum copeptin (as a surrogate marker for vasopressin) in patients with monosymptomatic nocturnal enuresis, and evaluated whether they are useful for predicting desmopressin treatment outcome. Materials and Methods: The study included 32 children 6 to 11 years old with monosymptomatic nocturnal enuresis and nocturnal polyuria. Exclusion criteria were daytime urinary symptoms and underlying diseases causing nocturnal enuresis. Subjects were treated with 120 mg or 240 mg desmopressin oral disintegrating tablet and were divided into responders (at 120 or 240 mg) and nonresponders (at 240 mg). Day/night ratios of plasma copeptin and urinary aquaporin 2 were measured during desmopressin treatment. Results: There was no significant difference in baseline day/night ratio of urinary aquaporin 2 between desmopressin responders and nonresponders. After 8 weeks of treatment there was a significant correlation between day/night ratio of aquaporin 2 and percentage of wet nights. In responders (but not nonresponders) there was a significant difference in the change in aquaporin 2 day/night ratio from before treatment to complete remission (p = 0.0004). For plasma copeptin the baseline day/night ratio for responders at 120 mg was significantly lower than in the 240 mg nonresponder group (p = 0.02). Conclusions: Urinary aquaporin 2 appears to be a biomarker of desmopressin treatment effectiveness during therapy, while plasma copeptin levels before treatment are predictive of desmopressin response.