Hypertonic saline stimulated copeptin reliably Diagnoses AVP deficiency in Polyuria Polydipsia Syndrome patients

A recent trial published in the New England Journal of Medicine shed light on the challenging diagnosis of arginine vasopressin (AVP) deficiency versus primary polydipsia, a puzzle in the field of water balance disorders. The study involved 158 adult patients and compared the diagnostic accuracy of two stimulation methods: hypertonic saline and arginine.

Out of the participants, 44% received a diagnosis of AVP deficiency, while 56% were diagnosed with primary polydipsia. The diagnostic accuracy was notably higher with hypertonic saline–stimulated copeptin (95.6%) compared to arginine-stimulated copeptin (74.4%). The estimated difference of -21.2 percentage points emphasizes the superiority of hypertonic saline in diagnosing AVP deficiency.

Interestingly, 72% of the participants expressed a preference for arginine testing over hypertonic saline, indicating a potential shift in the landscape of diagnostic preferences.

Adverse events associated with both tests were generally mild. Notably, arginine-stimulated copeptin at or below 3.0 pmol per liter demonstrated a specificity of 90.9% for diagnosing AVP deficiency. Conversely, levels exceeding 5.2 pmol per liter led to a diagnosis of primary polydipsia with a specificity of 91.4%.