Urea-stimulated copeptin: a novel diagnostic approach in polyuria polydipsia syndrome.

This article focuses on evaluating oral urea as a novel, practical diagnostic test to differentiate arginine vasopressin (AVP) deficiency from primary polydipsia by measuring copeptin, a stable surrogate marker of AVP secretion. In a randomized, placebo-controlled trial involving healthy adults and an open-label pilot study with patients diagnosed with AVP deficiency or primary polydipsia, oral urea ingestion significantly increased copeptin levels in healthy individuals and those with primary polydipsia but not in patients with AVP deficiency. A copeptin cut-off of 3.5 pmol/L at 120 minutes post-urea ingestion distinguished AVP deficiency from primary polydipsia with 92% sensitivity and specificity. The study suggests that oral urea testing is a safe, cost-effective, and accessible alternative to current complex diagnostic methods, potentially suitable for broader clinical use pending further validation.