Which investigation is considered definitive for confirming Wilson's disease?

A liver biopsy measuring copper concentration is considered the definitive investigation for confirming Wilson's disease. This test involves obtaining a small sample of liver tissue and analyzing it for copper content. In patients with Wilson's disease, there is usually an accumulation of copper in the liver, reflecting the body's inability to properly excrete copper due to a genetic defect in the ATP7B gene. The measurement of copper levels in the liver helps to establish a diagnosis beyond suspicion, especially when clinical symptoms and other tests hint at the condition.

While serum ceruloplasmin levels and 24-hour urinary copper excretion can provide supportive information, they are not definitive on their own. Serum ceruloplasmin levels are typically low in Wilson's disease but can vary due to other conditions. Similarly, while elevated urinary copper excretion can suggest Wilson's disease, it can also occur in other liver diseases and is not a conclusive test. Genetic testing can confirm the diagnosis by identifying mutations in the ATP7B gene, but it is primarily a supplemental method rather than a definitive investigation. Thus, the liver biopsy directly measuring copper concentration is central to confidently diagnosing Wilson's disease.