AVP and neurohypophyseal diabetes insipidus: At 90 min, a stimulated copeptin of > 6.0 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 92% (95% CI [0.84-1.00]) for diagnosing AVP deficiency.