Urinary excretion of copper in patient's with Wilson's disease is often quite high, but sometimes overlaps with that seen in patients with other diagnoses. Following a challenge dose of D-penicillamine there is a dramatic increase in urinary copper excretion for patient's with Wilson's disease but not with other diseases.
Dose of D-penicillamine used by Martins da Costa et al: 500 mg given just before starting a 24 hour urine collection, with a second dose given at 12 hours into the collection.
Specimen collection: 24 hour urine into a copper-free container
According to Muller et al, a urinary copper excretion after D-penicillamine challenge > 25 µmol/24 hours in 76% of patients with Wilson's disease and 6.6%.
According to Martins da Costa et al. there may be overlap for some patients with Wilson's disease and those with other disorders (see Figure 6, page 613).
24 Hour Urinary Copper Excretion After Challenge
Diagnosis of Wilson's Disease
> 37 µmol
definite
25.1 - 37 µmol
probable
19 - 25 µmol
possible
< 19 µmol
unlikely
Observations:
(1) The test is more sensitive in symptomatic patients.
(2) It may be helpful in children for whom the clinical diagnosis is equivocal (those who do not show Kaiser-Fleischer rings, etc).
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