title: On accuracy and precision of a HPLC method for measurement of urine porphyrin concentrations.
abstract: We studied the accuracy and precision of a HPLC method for determination of porphyrins in urine. A commercial standard solution appeared to contain less porphyrins than indicated by the manufacturer, since calibration resulted in lower concentrations of uroporphyrin and coproporphyrin: 16% and 8%, respectively. Coefficients of variation for the measurement of uro-, hepta-, copro I and copro III porphyrins in samples of patients with and without porphyria were often much less than 15%. Comparison of measurements with and without calibrated standards revealed differences for uroporphyrin and coproporphyrin of 27% and 5%, respectively. Recovery of added uroporphyrin and coproporphyrin was 99%. The main cause of the variability in test results was apparently the improperly calibrated standard solutions. The precision of porphyrin measurements was not influenced by the type of porphyria.
authors.affiliation: Department of Clinical Chemistry, Deventer Ziekenhuis, The Netherlands.
authors.forename: F M
authors.initials: FM
authors.lastname: Zuijderhoudt
authors.forename: S G
authors.initials: SG
authors.lastname: Koehorst
authors.forename: W E
authors.initials: WE
authors.lastname: Kluitenberg
authors.forename: J
authors.initials: J
authors.lastname: Dorresteijn-de Bok
mesh_terms: D002138:Calibration; D002624:Chemistry, Clinical / Q000379:methods*; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D003306:Coproporphyrins / Q000097:blood / Q000652:urine; D006801:Humans; D008107:Liver Diseases / Q000652:urine; D017119:Porphyria Cutanea Tarda / Q000652:urine; D011164:Porphyrias / Q000652:urine; D011166:Porphyrins / Q000652:urine*; D015203:Reproducibility of Results
chemical_list: D003306:Coproporphyrins; D011166:Porphyrins; C026971:coproporphyrin III