The sensitivity, specificity, PPV, and NPV of serum CP level for the diagnosis of WD at the conventional cutoff value <200 mg/L were 99.0, 80.9, 29.1, and 99.9%, respectively, in the whole group and 99.0, 76.4, 38.9, and 99.8%, respectively, in patients with liver, nervous, and mental diseases (Tables 4 and 5). This evidence concerns the gene CP and Wilson disease.