Long-Term Urinary Copper Excretion and Exchangeable Copper in Children With Wilson Disease Under Chelation Therapy

Serum ceruloplasmin oxidase activity: A neglected diagnostic biomarker for Wilson disease

BACKGROUND

Low serum ceruloplasmin concentration is considered robust marker for Wilson disease (WD) screening, measuring serum ceruloplasmin oxidase activity might be an even more valuable diagnostic tool, but it has not been sufficiently studied.

METHODS

All patients who were assessed for serum ceruloplasmin oxidase activity between January 1, 2016, and September 2, 2019, were enrolled in this study. The diagnostic performance of serum ceruloplasmin oxidase activity was analyzed using receiver operating characteristic curve analysis (ROC), Spearman's rank correlation, and Mann-Whitney U test.

RESULTS

Serum ceruloplasmin oxidase activity was significantly decreased in WD patients (0.87 U/L, IQR 0.61-1.54). The optimal cut-off of serum ceruloplasmin oxidase activity to identified WD is 7 U/L, with sensitivity and specificity of 97.03 % and 98.19 %, respectively. Furthermore, this study revealed a positive correlation between enzymatic and immunoreactive serum ceruloplasmin tests. As primary diagnostic methods, serum ceruloplasmin levels below the diagnostic cut-offs for either the enzymatic or immunoreactive tests were observed in 818 out of 842 WD patients (97.15 %). Compared with the presence of K-F rings in asymptomatic patients, the accuracy of serum ceruloplasmin tests was significantly higher (56.12 % VS 95.08 %). Moreover, the positive rate of cranial MRI in neurological patients was similar to the tests of serum ceruloplasmin (92.91 % VS 97.40 %). Moreover, 71 patients had ambiguous genetic results, complicating the diagnosis. However, serum ceruloplasmin tests successfully identified 65 out of these 71 patients (91.55 %).

CONCLUSION

Serum ceruloplasmin oxidase activity has excellent performance in diagnosing WD, which should be widely used as preferred test in WD patients.

Exchangeable copper for patients with Wilson disease at follow-up: Rethinking normal ranges or changing methodology

BACKGROUND AND AIM

Determining suitable copper parameters for monitoring Wilson disease remains a topic of ongoing discussion. International recommendations currently rely on the combination of urinary copper excretion and nonspecific liver markers when considering therapy and time elapsed since diagnosis. The emergence of exchangeable copper (CuEX) as a novel measurement reflecting the "free copper pool" held promise as a valuable target to ensure metabolic stability during follow-up, although the validation of target ranges remains unknown. We aimed to evaluate CuEX quantification in repeated samples from 92 real-world patients with Wilson disease during a 2-year period.

APPROACH

Patients were classified as "stable" if a diagnosis had been made more than 1 year before and were compliant with stable anti-copper drug and dose. Otherwise, patients were classified as "nonstable."

RESULTS

Two hundred and thirteen CuEX samples were obtained per clinical practice. Overall, 57% of CuEX measurements fell below the reference "range of normality," whereas only 34% were within and 9% were above normal levels. There was no association of CuEX levels with therapy, elapsed time from diagnosis, or clinical stability, although most of the samples above normality corresponded to nonstable patients. Only 23.4% of the CuEX samples were aligned with data obtained from concomitant urinary copper excretion.

CONCLUSIONS

Our findings suggest that CuEX is a suboptimal tool for assessing copper homeostasis when used alone and should be used with caution if no additional information is available. Normal reference intervals for Wilson disease-treated patients should be redefined, as most CuEX quantifications fell in the lower range, with no sign of overtreatment in these patients.

Non-ceruloplasmin copper and urinary copper in clinically stable Wilson disease: Alignment with recommended targets

Background & Aims

Wilson disease (WD) is caused by accumulation of copper primarily in the liver and brain. During maintenance therapy of WD with D-penicillamine, current guidelines recommend on-treatment ranges of urinary copper excretion (UCE) of 200-500 μg/24 h and serum non-ceruloplasmin-bound copper (NCC) of 50-150 μg/L. We compared NCC (measured by two novel assays) and UCE from patients with clinically stable WD on D-penicillamine therapy with these recommendations.

Methods

This is a secondary analysis of data from the Chelate trial (NCT03539952) that enrolled physician-selected patients with clinically stable WD on D-penicillamine maintenance therapy (at an unaltered dose for at least 4 months). We analyzed laboratory samples from the first screening visit, prior to interventions. NCC was measured by either protein speciation (NCC-Sp) using anion exchange high-performance liquid chromatography protein speciation followed by copper determination with inductively coupled plasma mass spectroscopy or as exchangeable copper (NCC-Ex). NCC-Sp was also analyzed in healthy controls (n = 75).

Results

In 76 patients with WD with 21.3±14.3 average treatment-years, NCC-Sp (mean±SD: 56.6±26.2 μg/L) and NCC-Ex (mean±SD: 57.9±24.7 μg/L) were within the 50-150 μg/L target in 61% and 54% of patients, respectively. In addition, 36% and 31%, respectively, were even below the normal ranges (NCC-Sp: 46-213 μg/L, NCC-Ex: 41-71 μg/L). NCC-Ex positively correlated with NCC-Sp (r2 = 0.66, p <0.001) but with systematic deviation. UCE was outside the 200-500 μg/24 h target range in 58%. Only 14/69 (20%) fulfilled both the NCC-Sp and UCE targets. Clinical or biochemical signs of copper deficiency were not detected.

Conclusion

Clinically stable patients with WD on maintenance D-penicillamine therapy frequently have lower NCC-Sp or higher UCE than current recommendations without signs of overtreatment. Further studies are warranted to identify appropriate target ranges of NCC-Sp, NCC-Ex and UCE in treated WD.

Impact and implications

Chelator treatment of patients with Wilson disease (WD) is currently guided by measurements of non-ceruloplasmin-bound copper (NCC) and 24 h urinary copper excretion (UCE) but validation is limited. In 76 adults with ≈21 years history of treated WD and clinically stable disease on D-penicillamine therapy, NCC was commonly found to be below normal values and recommended target ranges whether measured by protein speciation (NCC-Sp) or as exchangeable copper (NCC-Ex), while UCE values were above the recommended target range in 49%. Common wisdom would suggest overtreatment in these cases, but no clinical or biochemical signs of copper deficiency were observed. Exploratory analysis of liver enzymes suggested that NCC below levels seen in controls may be beneficial, while the relation to UCE was less clear. The data calls for critical re-evaluation of target ranges for treatment of WD, specific for drug and laboratory methodology.

Clinical trial number

(NCT03539952).

Recent advances in the diagnosis and management of Wilson's disease

In this editorial, the reader will be updated on novel epidemiological, diagnostic, and therapeutical proposals in the field of Wilson disease.

Benefits of using exchangeable copper and the ratio of exchangeable copper in a real-world cohort of patients with Wilson disease

Wilson disease (WD) is a complex disease in which diagnosis and long-term metabolic copper control remains challenging. The absence of accurate biomarkers requires the combination of different parameters to ensure copper homeostasis. Exchangeable copper and its ratio (REC) have been suggested to be useful biomarkers in this setting. We aimed at introducing these measurements and evaluate their performance and accuracy in our real-world cohort of WD patients. Exchangeable copper and REC were measured in 48 WD patients and 56 control individuals by inductively coupled plasma-mass-spectrometry. Demographic and clinical characteristics were collected. REC was shown to be significantly higher among WD patients compared to controls and useful for WD identification by using the previously established cutoffs: 71.4% of WD patients with a recent diagnosis had REC ≥18.5% and 95.1% of long-term treated WD had REC ≥14%; only four patients of the cohort presented discordant levels. Moreover, REC values were below 15% in all the control individuals. Exchangeable copper was significantly higher in WD patients compared to controls and tended to be reduced among WD patients who were compliant to medication. This real-life study confirmed that exchangeable copper and REC are useful serum biomarkers that can be used as complementary tests to ensure WD diagnosis (REC) and copper homeostasis whithin time (exchangeable copper). The desirable target levels for this last objective still needs to be validated in prospective cohorts.

Wilson Disease and Alpha1-Antitrypsin Deficiency: A Review of Non-Invasive Diagnostic Tests

Wilson disease and alpha1-antitrypsin deficiency are two rare genetic diseases that may impact predominantly the liver and/or the brain, and the liver and/or the lung, respectively. The early diagnosis of these diseases is important in order to initiate a specific treatment, when available, ideally before irreversible organ damage, but also to initiate family screening. This review focuses on the non-invasive diagnostic tests available for clinicians in both diseases. These tests are crucial at diagnosis to reduce the potential diagnostic delay and assess organ involvement. They also play a pivotal role during follow-up to monitor disease progression and evaluate treatment efficacy of current or emerging therapies.

The Role of Zinc in the Treatment of Wilson’s Disease

Wilson’s disease (WD) is a hereditary disorder of copper metabolism, producing abnormally high levels of non-ceruloplasmin-bound copper, the determinant of the pathogenic process causing brain and hepatic damage and dysfunction. Although the disease is invariably fatal without medication, it is treatable and many of its adverse effects are reversible. Diagnosis is difficult due to the large range and severity of symptoms. A high index of suspicion is required as patients may have only a few of the many possible biomarkers. The genetic prevalence of ATP7B variants indicates higher rates in the population than are currently diagnosed. Treatments have evolved from chelators that reduce stored copper to zinc, which reduces the toxic levels of circulating non-ceruloplasmin-bound copper. Zinc induces intestinal metallothionein, which blocks copper absorption and increases excretion in the stools, resulting in an improvement in symptoms. Two meta-analyses and several large retrospective studies indicate that zinc is equally effective as chelators for the treatment of WD, with the advantages of a very low level of toxicity and only the minor side effect of gastric disturbance. Zinc is recommended as a first-line treatment for neurological presentations and is gaining acceptance for hepatic presentations. It is universally recommended for lifelong maintenance therapy and for presymptomatic WD.