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.

CONCLUSION

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