AVP and neurohypophyseal diabetes insipidus: At 90 min, a stimulated copeptin of > 6.0 pmol/l provided a specificity of 97% (95% CI [0.92-1.00]) and sensitivity of 65% (95% CI [0.53–0.77]) for diagnosing primary polydipsia, correctly diagnosing 64% (n = 37/58) of patients with primary polydipsia and falsely diagnosing 3% (n = 1/38) patients with AVP deficiency.