Biochemical diagnosis of Wilson's disease: an update

Abstract

Wilson's disease (WD) is an inherited disorder of copper metabolism caused by mutations in the ATP7B gene. This condition is characterized by the accumulation of copper in the liver and other organs and tissues causing hepatic and neuropsychiatric manifestations. This paper reviews the diagnostic performance and limitations of the biochemical tests commonly used to detect this underdiagnosed disease. It also provides some recommendations and suggests a set of standardized laboratory comments. At present, a rapid, simple, reliable biochemical test that confirms diagnosis of WD is not available. However, diagnosis can be established based on serum ceruloplasmin and urinary copper excretion. Total serum copper should be employed with caution, since it has a low negative predictive value. The use of estimated non-ceruloplasmin-bound copper is not recommended. Nevertheless, measured relative exchangeable copper has very high sensitivity and specificity and emerges as a potential gold standard for the biochemical diagnosis of WD. The development of novel assays for WD detection makes this disorder a potential candidate to be included in newborn screening programs.

Keywords: ATP7B gene; Wilson’s disease; ceruloplasmin; copper.

Figure 1:

Algorithm for biochemical diagnosis of Wilson’s disease (WD). Total serum copper concentration <0.8 μmol/dL in the presence of intermediate ceruloplasmin concentrations (0.1–0.2 g/L) grounds suspicion of a very likely case of WD (because total serum copper has a high positive predictive value). A relative exchangeable copper (REC) result >18.5% or intrahepatic copper concentrations >4 μmol/g in the absence of cholestasis is suggestive of a very likely case of WD. *Genetic testing is strongly indicated in patients with laboratory results suggestive of a very likely case of WD or in patients with laboratory results suggestive of likely WD in whom a liver biopsy is to be avoided.