Measurement of urinary porphyrins and porphyrin precursors in Dutch hospital laboratories: a review of quality control over 5 years.
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.
Zuijderhoudt
Floris M J
FM
Department of Clinical Chemistry, Deventer Hospital, 7400 GC Deventer, The Netherlands. zuijderf@wanadoo.nl
Weykamp
Cas W
CW
Willems
Hans L
HL
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
D003306:Coproporphyrins; D011166:Porphyrins; D014578:Uroporphyrins; D011162:Porphobilinogen; D000622:Aminolevulinic Acid