Relative exchangeable copper: A new highly sensitive and highly specific biomarker for Wilson's disease diagnosis

► A rapid and reliable biological test for Wilson disease (WD) diagnosis is still needed. ► Excheangeable Copper (CuEXC) determination revealed to be stable and analytically reliable. ► Relative exchangeable copper (REC=CuEXC/total copper %) is a new biomarker for diagnois of WD. ► REC has 100% specificity and 100% sensitivity in diagnosis of WD.