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.

Analysis of Urinary Porphyrins by High Performance Liquid Chromatography-Electrospray Ionization Mass Spectrometry

“…Levels of CP in the patient urines were observed about two times higher than those of healthy persons. The significant increase of CP in patient urine was consistent with that previously reported for patients with liver disease, [46] indicating that the determination of CP in human urine might be served as a diagnostic symptom of liver disease. It was also observed that the levels of HEXAP and PENTAP in the patient urine samples were significantly higher than those in healthy human urine.…”

Measurement of urinary porphyrins and porphyrin precursors in Dutch hospital laboratories: a review of quality control over 5 years

“…For URO this has been shown before. 4 Using these results, we conclude that commutable calibrators are needed to improve the laboratory diagnosis of porphyria. Using such calibrators the inter-laboratory CVs should decrease.…”