On accuracy and precision of a HPLC method for measurement of urine porphyrin concentrations.
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.
Zuijderhoudt
F M
FM
Department of Clinical Chemistry, Deventer Ziekenhuis, The Netherlands.
Koehorst
S G
SG
Kluitenberg
W E
WE
Dorresteijn-de Bok
J
J
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
D003306:Coproporphyrins; D011166:Porphyrins; C026971:coproporphyrin III