The optimal threshold of serum ceruloplasmin in the diagnosis of Wilson’s disease: A large hospital-based study

BACKGROUND AND AIMS A ceruloplasmin (CP) concentration <200 mg/L is conventionally considered as one of the major diagnostic criteria for Wilson's disease (WD). However, the diagnostic accuracy of this threshold has never been investigated in a sufficiently large group of patients. This study aims to present the results of serum CP measurements in various patients and to identify the optimal cutoff value of CP for the diagnosis of WD. MATERIALS AND METHODS We identified patients whose CP levels were evaluated from January 1, 2016 to December 31, 2016 using a laboratory information database. Data related to CP measurement were retrieved. We carefully reviewed patients' electronic medical records to correct errors and to obtain other necessary data. Data related to WD were retrieved from a special document containing medical records of patients with WD, which were created, modified, and maintained by authors. RESULTS CP level was determined in 4048 patients (WD, 297; non-WD, 3751). The mean serum CP level in patients with WD was 50.6±44.2 mg/L, which was significantly lower than that in non-WD patients (293.2±117.3 mg/L, p<0.001). Only 1.0% of patients with WD had CP ≥200 mg/L. The sensitivity and specificity of CP for the diagnosis of WD were 99.0 and 80.9%, respectively, for the conventional cutoff value <200 mg/L and 95.6 and 95.5%, respectively, for the cutoff value <150 mg/L; the latter provided a higher diagnostic accuracy for WD. 53.0% of patients with liver failure, 37.7% of patients with nephrotic syndrome, and 23.0% of patients age 1 to 6 months had serum CP <200 mg/L. Patients who were pregnant and those with malignant tumors, and infectious and inflammatory diseases had significantly higher mean serum CP levels. CONCLUSION The optimal cutoff value of CP for the diagnosis of WD in China is 150 mg/L, with a sensitivity of 95.6% and specificity of 95.5%, thereby providing the highest diagnostic accuracy for WD.