American Board of Psychiatry and Neurology (ABPN) Practice Exam 2026 - Free ABPN Practice Questions and Study Guide

In diagnosing Wilson's disease, serum ceruloplasmin level is the test of choice due to its specific role in copper metabolism. Wilson's disease is a genetic disorder that leads to excessive accumulation of copper in the body, primarily affecting the liver and brain. Ceruloplasmin, a copper-carrying protein synthesized by the liver, typically has lower levels in individuals with Wilson's disease due to impaired copper incorporation.

A low serum ceruloplasmin level is a significant finding in patients suspected of having Wilson's disease, as it reflects the body’s inability to properly transport copper, which is a hallmark of the condition. Moreover, while serum copper levels and urine copper excretion can also be assessed, they are less reliable as standalone diagnostic tests compared to ceruloplasmin levels.

The other options provided do not directly relate to the diagnosis of Wilson's disease. Serum ACE levels are more relevant in conditions such as sarcoidosis. Chromosomal analysis for CAG triplet repeats is used for diagnosing Huntington’s disease, which is unrelated to Wilson's disease. A lumbar puncture for CSF titer generally pertains to neurological evaluations or infections, not to diagnoses of metabolic disorders like Wilson’s disease. Thus, serum ceruloplasmin remains the cornerstone test