AVP and neurohypophyseal diabetes insipidus: At 90 min, a stimulated copeptin of ≤ 3.0 pmol/l provided a sensitivity of 64% (95% CI [0.47–0.78]) and specificity of 95% (95% CI [0.88-1.00]) for diagnosing AVP deficiency, falsely diagnosing 5% (n = 3/58) of patients with primary polydipsia and correctly diagnosing 61% (n = 23/38) patients with AVP deficiency.