1. IS CERULOPLASMIN A GOLD ENOUGH STANDARD FOR COPPER OVERLOAD?
Victor Tseng, MD
Resident Journal Club
April 2014, AVAMC

2. Bile (Enterohepatic Ciculation)
Enterocyte
2 mg/d
Hepatocyte
ATP7B
Portal Circulation
Cp-(Cu2+)n
Peripheral Blood

3. Serum Ceruloplasmin is…
Spuriously decreased when there is
Spuriously increased when there is
Diminished Synthetic Capacity
Cirrhosis/ESLD
Congenital Aceruloplasminemia
Chronic Hepatitis
Increased Elimination
Nephrotic Syndrome/Proteinuria
Protein-Losing Enteropathy
X-Linked Menkes
True Copper Deficiency
TPN
Gastric Bypass
Divalent Chelation (Penacillamine)
Hepatocellular Injury
Acute on Chronic Hepatitis
Heterozygosity
Attenuated Compound Heterozygotes
Asymptomatic Carriers
Hyperestrogenism
HRT/C
Pregnancy
Inflammation (Acute Phase Reactant)

4. WHICH OF THESE CRITERIA PROVIDES A DEFINITIVE DIAGNOSIS?
Liver biopsy with [Cu2+] > 50 µg/g in whole tissue homogenate
Triad: neuro/ψ s/sx + serum Cp < 20 mg/dL + urinary Cu2+ > 100 µg/d
Triad: KF rings + neuro/ψ s/sx + serum Cp < 20 mg/dL
Liver biopsy with positive copper stain and characteristic histopathology
Allele-specific genetic testing
None of the above

5. WHICH ONE IS A KAYSER-FLEISCHER RING?

7. CLINICAL QUESTIONS OF THE STUDY
What was the rate of adherence to AASLD guidelines for assaying serum ceruloplasmin as a screen of Wilson Disease?
QUESTION 2
Under these screening practices, what were the test characteristics?

8. ≤ 40
≥ 56
2178 (7)
1781 (1)
1064 (0)
5011 12
Known WD
Cp < 20 mg/dL
Cp ≥ 20 mg/dL
424
4599 8
416
4599
“Confirmed” New WD

9. Can you see the problem? 424 37 387 Cp < 20 mg/dL
“Confirmatory Testing”
(UCu2+ or Liver Biopsy)
Workup Terminated
(possibly other diagnosis made)
Can you see the problem?

11. CONFUSION MATRIX – ALL PATIENTS (5023)
mg/dL
WD “Confirmed”
WD Ruled Out
Total
Cp < 20 8
416
424
Cp ≥ 20
4599
5015
5023 TP FP FN TN

12. DESCRIPTIVE STATISTICS – ALL PATIENTS
Prevalence (Pre-Test) = 8/5023 = 0.16%
Se = TP/(TP + FN) = 8/(8 + 0) = 1.0
Sp = TN/(TN + FP) = 4599/( ) = 0.917
PPV = TP/(TP + FP) = 8/424 = 0.019
NPV = TN/(TN + FN) = 4599/4599 = 1.0
LR+ = Se/(1 – Sp) = 1.0/(1 – 0.917) = 12
LR- = (1 – Se)/Sp = 0
NNDx = Total/TP = 5023/8 = 627

13. BAYSIAN NOMOGRAM – ALL PATIENTS
LR+ = 12
LR- = 0

14. STUDY LIMITATIONS Two major sources of bias are present here
Verification Bias: Gold standard confirmatory testing or chart review was not applied equally regardless of serum Cp result
Spectrum Bias: Serum Cp is known to vary with presentation of disease (e.g. fulminant hepatic failure vs hemolytic crisis vs asymtomatic transaminitis)

15. MORE STUDY LIMITATIONS
Ultimately, the paper was designed to explore an epiphenomenon related to testing practices.
The paper was not intended to assess the validity of a diagnostic test (serum Cp) or determine receiver-operative curves.

16. BOTTOM LINE
A positive serum Cp test confers a change of probability of 0.16% to around 2%
Ignoring verification bias, a negative serum Cp appears to rule out Wilson’s (perfect sensitivity)
Testing according to AASLD age guidelines does not change the test performance much
Testing serum Cp does not change further workup or management in > 90% of cases.

17. IMPORTANT UNANSWERED QUESTIONS
How good is the test when applied to patients after exclusion of other causes of hepatic disease?
QUESTION 4
How does the test fare in different manifestations of Wilson’s Disease?

18. THE BIG QUESTION
Wilson’s Disease is rare. Do we really need screening tests for rare diseases?
Can you think of any rare and treatable diseases for which we implement generalized or targeted screening?