What is the role of the Ceruloplasmin (CP) test in diagnosing Wilson's disease in patients with unexplained liver disease, neurological symptoms, or psychiatric issues, particularly those with a family history of the condition?

Ceruloplasmin Testing in Wilson's Disease

Serum ceruloplasmin should be routinely measured in all patients aged 3-55 years with unexplained liver disease, neurological symptoms, or psychiatric abnormalities, but a normal ceruloplasmin level does NOT exclude Wilson's disease and requires additional diagnostic testing. 1

Critical Diagnostic Limitations

The ceruloplasmin test has significant limitations that every clinician must understand:

• 15-36% of children with Wilson's disease have ceruloplasmin in the normal range 2
• Up to 50% of patients with hepatic Wilson's disease may have low-normal ceruloplasmin levels 2
• In one series, 22% of Wilson's disease patients (12 of 55) had normal ceruloplasmin AND no Kayser-Fleischer rings 2
• The positive predictive value of low ceruloplasmin alone is only 5.9-6%, meaning most patients with low ceruloplasmin do NOT have Wilson's disease 1, 2, 3

When to Order Ceruloplasmin

Order ceruloplasmin testing in these specific clinical scenarios:

Hepatic Presentations

• Unexplained elevated aminotransferases at any age 3-55 years 1, 2
• Isolated hepatomegaly or fatty liver of unknown cause 2
• Cirrhosis without clear etiology 2
• Fulminant hepatic failure 2, 4
• Autoimmune hepatitis failing standard immunosuppressive therapy 2

Neurological Presentations

• Tremor, dystonia, dysarthria, or drooling 1, 2
• Movement disorders or coordination problems 2
• Deteriorating handwriting (micrographia) 1
• Behavioral deterioration or declining school performance 1

Psychiatric Presentations

• Depression, anxiety, or personality changes with ANY liver abnormality 1, 2
• Frank psychosis in young adults 1

Other Presentations

• Unexplained Coombs-negative hemolytic anemia with liver dysfunction 2, 4
• First-degree relatives of confirmed Wilson's disease patients 2

Interpreting Ceruloplasmin Results

Extremely Low Levels (<50 mg/L or <5 mg/dL)

• Provides strong evidence for Wilson's disease and warrants immediate comprehensive evaluation 1, 2

Modestly Low Levels (<200 mg/L or <20 mg/dL but >50 mg/L)

• Suggests further evaluation is necessary but is NOT diagnostic 1
• Approximately 20% of heterozygous carriers (who do NOT have disease) have decreased ceruloplasmin 1, 2

Normal Levels (≥200 mg/L or ≥20 mg/dL)

• Does NOT exclude Wilson's disease 1, 2
• Must proceed with additional diagnostic testing if clinical suspicion remains 2

Essential Follow-Up Testing When Ceruloplasmin is Abnormal OR Clinical Suspicion Remains High

Proceed with this diagnostic algorithm:

1. 24-hour urinary copper excretion (using copper-free glassware)

   • Values >100 μg/24 hours (>1.6 μmol/24 hours) indicate Wilson's disease 2

2. Calculate non-ceruloplasmin-bound (free) copper

   • Values >25 μg/dL (250 μg/L) strongly suggest Wilson's disease 2

3. Slit-lamp examination by experienced ophthalmologist

   • Look for Kayser-Fleischer rings 1
   • Absence does NOT exclude diagnosis, even in neurological disease 1

4. Consider genetic testing for ATP7B mutations

   • Two pathogenic mutations confirm diagnosis 2

5. Hepatic copper concentration if liver biopsy performed

   • 4 μmol/g dry weight (>250 μg/g) provides best biochemical evidence 2

Critical Pitfalls to Avoid

False Elevation of Ceruloplasmin

• Ceruloplasmin is an acute phase reactant and can be falsely elevated by 1, 2:
  • Acute inflammation or infection
  • Pregnancy
  • Estrogen supplementation or oral contraceptives

Assay Limitations

• Immunologic assays may overestimate ceruloplasmin because they measure both apo- and holoceruloplasmin (only holoceruloplasmin contains copper) 1, 2
• Enzymatic assays measuring oxidase activity are more specific than immunologic assays 5

Age-Related Variations

• Ceruloplasmin is physiologically very low in infancy (up to 6 months), peaks above adult levels in early childhood, then normalizes 1, 2
• Age alone should NEVER exclude Wilson's disease from consideration 1, 2

Other Causes of Low Ceruloplasmin

Low ceruloplasmin occurs in conditions OTHER than Wilson's disease 1, 2:

• Severe protein loss (nephrotic syndrome, protein-losing enteropathy)
• End-stage liver disease of any etiology
• Copper deficiency (parenteral nutrition without trace elements)
• Menkes disease (X-linked copper transport disorder)
• Aceruloplasminemia (presents with hemosiderosis, not copper accumulation)

Impact on Morbidity and Mortality

Early diagnosis through appropriate ceruloplasmin testing and comprehensive evaluation is critical because:

• Wilson's disease is fatal if untreated but has excellent outcomes with early copper chelation therapy 6
• Delayed diagnosis leads to irreversible neurological damage and end-stage liver disease 4, 6
• Only 65% of patients presenting with liver disease are diagnosed by typical findings (low ceruloplasmin + Kayser-Fleischer rings), compared to 90% with neurological disease 4