AVP and neurohypophyseal diabetes insipidus: At 60 min after arginine infusion, a copeptin level ≤ 3.0 pmol/L showed a specificity of 95% (95% CI: 0.88-1.00) for AVP deficiency, while a copeptin level > 5.2 pmol/L demonstrated a specificity of 97% (95% CI: 0.92-1.00) for primary polydipsia.