AVP and neurohypophyseal diabetes insipidus: In the subset of patients undergoing additional hypertonic saline stimulation test (n = 60 out of 96), at 60 min, a stimulated copeptin of > 5.2 pmol/l provided a specificity of 100% (95% CI [0.99-1.00]) for diagnosing primary polydipsia and a stimulated copeptin of ≤ 3.0 pmol/l provided a specificity of 95% (95% CI [0.86-1.00]) for diagnosing AVP deficiency.