title: Measurement of urinary porphyrins and porphyrin precursors in Dutch hospital laboratories: a review of quality control over 5 years.
abstract: BACKGROUND
  We evaluated a quality control scheme for the measurement of urinary uroporphyrin, coproporphyrin, total urinary porphyrins and precursors of urinary porphyrins, delta-aminolevulinic acid and porphobilinogen that was performed in The Netherlands during a period of 5 years.
  
  
  METHODS
  Six quality control samples were distributed each year to the participating laboratories. Mean concentrations and the corresponding coefficients of variation were calculated.
  
  
  RESULTS
  Coefficients of variation varied widely and were very high in the concentration ranges that can be found in patients with low-grade porphyria.
  
  
  CONCLUSIONS
  Commutable calibrators are needed to improve the laboratory diagnosis of porphyria.
authors.affiliation: Department of Clinical Chemistry, Deventer Hospital, 7400 GC Deventer, The Netherlands. zuijderf@wanadoo.nl
authors.forename: Floris M J
authors.initials: FM
authors.lastname: Zuijderhoudt
authors.forename: Cas W
authors.initials: CW
authors.lastname: Weykamp
authors.forename: Hans L
authors.initials: HL
authors.lastname: Willems
mesh_terms: D000622:Aminolevulinic Acid / Q000652:urine; D019963:Clinical Chemistry Tests / Q000592:standards*; D003306:Coproporphyrins / Q000652:urine; D006801:Humans; D007755:Laboratories, Hospital; D009426:Netherlands; D011162:Porphobilinogen / Q000652:urine; D011166:Porphyrins / Q000652:urine*; D011786:Quality Control; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014578:Uroporphyrins / Q000652:urine
chemical_list: D003306:Coproporphyrins; D011166:Porphyrins; D014578:Uroporphyrins; D011162:Porphobilinogen; D000622:Aminolevulinic Acid