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. CONCLUSION: Commutable calibrators are needed to improve the laboratory diagnosis of porphyria.