Long-term evaluation of urinary copper excretion and non-caeruloplasmin associated copper in Wilson disease patients under medical treatment.

OBJECTIVE: Urinary copper excretion rates and non-caeruloplasmin associated copper concentrations are increased in patients with Wilson disease. However, there is little literature describing the monitoring of these parameters over the long term.
METHODS: This is a monocentric retrospective study including data collected between 2003 and 2015 from 321 patients with Wilson disease by chart review. The patients were under therapy with D-penicillamine, trientine, or zinc. 24-h urinary copper excretion rates, non-caeruloplasmin associated copper, and total serum copper concentrations were determined at the start of therapy, as well as 6, 12, 18, 24, 36, and ≥ 60 months after the start of therapy. For patients taking chelating agents, all parameters were measured while under continued therapy, as well as after a 48-h dose interruption. A mathematical formula to predict 24-h urinary copper excretion rates under different therapies was established.
RESULTS: In all treatment groups, urinary copper excretion rates decreased over time, but the inter-individual variation of the results was high. Non-caeruloplasmin associated copper concentrations tended to decline over time, but with a higher variation of results than that observed for urinary copper excretion rates.
CONCLUSION: Due to their variability, urinary copper excretion rates and serum copper concentrations are less than ideal parameters by which to monitor the benefit of a copper-reducing therapy. Urinary copper excretion rates seem to be more suitable than non-caeruloplasmin associated copper concentrations for this purpose.