Serum ceruloplasmin oxidase activity: A neglected diagnostic biomarker for Wilson disease

Low serum ceruloplasmin concentration is considered robust marker for Wilson disease (WD) screening, measuring serum ceruloplasmin oxidase activity might be an even more valuable diagnostic tool, but it has not been sufficiently studied.

All patients who were assessed for serum ceruloplasmin oxidase activity between January 1, 2016, and September 2, 2019, were enrolled in this study. The diagnostic performance of serum ceruloplasmin oxidase activity was analyzed using receiver operating characteristic curve analysis (ROC), Spearman's rank correlation, and Mann-Whitney U test.

Serum ceruloplasmin oxidase activity was significantly decreased in WD patients (0.87 U/L, IQR 0.61-1.54). The optimal cut-off of serum ceruloplasmin oxidase activity to identified WD is 7 U/L, with sensitivity and specificity of 97.03 % and 98.19 %, respectively. Furthermore, this study revealed a positive correlation between enzymatic and immunoreactive serum ceruloplasmin tests. As primary diagnostic methods, serum ceruloplasmin levels below the diagnostic cut-offs for either the enzymatic or immunoreactive tests were observed in 818 out of 842 WD patients (97.15 %). Compared with the presence of K-F rings in asymptomatic patients, the accuracy of serum ceruloplasmin tests was significantly higher (56.12 % VS 95.08 %). Moreover, the positive rate of cranial MRI in neurological patients was similar to the tests of serum ceruloplasmin (92.91 % VS 97.40 %). Moreover, 71 patients had ambiguous genetic results, complicating the diagnosis. However, serum ceruloplasmin tests successfully identified 65 out of these 71 patients (91.55 %).

Serum ceruloplasmin oxidase activity has excellent performance in diagnosing WD, which should be widely used as preferred test in WD patients.