title: Urinary copper/zinc ratio: a promising parameter for replacement of 24-hour urinary copper excretion for diagnosis of Wilson's disease in children.
abstract: BACKGROUND
  Although 24-hour urinary copper excretion is valuable for diagnosis of Wilson's disease, accurate, timed collection entails practical difficulties. This study aimed to investigate the feasibility of morning urinary copper/creatinine or copper/zinc ratio as replacement parameter for diagnosing Wilson's disease.
  
  
  METHODS
  Five random urinary samples collected during 24 hours from two inpatients were used to estimate the consistency of urinary copper/creatinine and copper/zinc ratios. The correlation of the ratios with 24-hour urinary copper excretion was studied in 15 patients with liver diseases. The diagnostic value of morning urinary copper/zinc ratio was further studied in 9 children with Wilson's disease and 22 children with other liver diseases.
  
  
  RESULTS
  The coefficients of variation of urinary copper/creatinine and copper/zinc ratios during 24 hours were 12.5% and 9.3% respectively. The morning urinary copper/creatinine ratio, copper/zinc ratio, and 24-hour urinary copper excretion were correlated well. The area under receiver-operating characteristic curve was comparable between the morning urinary copper/zinc ratio and 24-hour urinary copper excretion (0.983 vs. 0.977).
  
  
  CONCLUSIONS
  Morning urinary copper/zinc ratio seems to be a promising parameter in replacement of 24-hour urinary copper excretion for diagnosis of Wilson's disease.
authors.affiliation: The Center for Pediatric Liver Diseases, Children's Hospital of Fudan University, Minhang District, Shanghai, China. jshwang@shmu.edu.cn
authors.forename: Jian-She
authors.initials: JS
authors.lastname: Wang
authors.forename: Yi
authors.initials: Y
authors.lastname: Lu
authors.forename: Xiao-Hong
authors.initials: XH
authors.lastname: Wang
authors.forename: Qi-Rong
authors.initials: QR
authors.lastname: Zhu
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D003300:Copper / Q000652:urine*; D003404:Creatinine / Q000652:urine; D005240:Feasibility Studies; D005260:Female; D006527:Hepatolenticular Degeneration / Q000175:diagnosis*; D006801:Humans; D008297:Male; D012372:ROC Curve; D013997:Time Factors; D015032:Zinc / Q000652:urine*
chemical_list: D003300:Copper; D003404:Creatinine; D015032:Zinc