Rapid and reliable diagnosis of Wilson disease using X‐ray fluorescence

Wilson's disease (WD) is a rare autosomal recessive disease due to mutations of the gene encoding the copper‐transporter ATP7B. The diagnosis is hampered by the variability of symptoms induced by copper accumulation, the inconstancy of the pathognomonic signs and the absence of a reliable diagnostic test. We investigated the diagnostic potential of X‐ray fluorescence (XRF) that allows quantitative analysis of multiple elements. Studies were performed on animal models using Wistar rats (n = 10) and Long Evans Cinnamon (LEC) rats (n = 11), and on human samples including normal livers (n = 10), alcohol cirrhosis (n = 8), haemochromatosis (n = 10), cholestasis (n = 6) and WD (n = 22). XRF experiments were first performed using synchrotron radiation to address the elemental composition at the cellular level. High‐resolution mapping of tissue sections allowed measurement of the intensity and the distribution of copper, iron and zinc while preserving the morphology. Investigations were further conducted using a laboratory X‐ray source for irradiating whole pieces of tissue. The sensitivity of XRF was highlighted by the discrimination of LEC rats from wild type even under a regimen using copper deficient food. XRF on whole formalin‐fixed paraffin embedded needle biopsies allowed profiling of the elements in a few minutes. The intensity of copper related to iron and zinc significantly discriminated WD from other genetic or chronic liver diseases with 97.6% specificity and 100% sensitivity. This study established a definite diagnosis of Wilson's disease based on XRF. This rapid and versatile method can be easily implemented in a clinical setting.