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Stability of porphyrins and porphyrin precursors in urine and plasma samples: implications for sample handling and storage
  1. Claire J Gallagher1,2,
  2. Lucy-Anne Bentley1,2,
  3. Rhiannon Challenger1,2,
  4. Martyn Jones1,2,
  5. Danja Schulenburg-Brand1,3
  1. 1Cardiff Porphyria Service, University Hospital of Wales, Cardiff, UK
  2. 2Department of Medical Biochemistry and Immunology, University Hospital of Wales, Cardiff, UK
  3. 3Department of Haematology, Immunology and Metabolic Medicine, University Hospital of Wales, Cardiff, UK
  1. Correspondence to Mrs Claire J Gallagher, Cardiff Porphyria Service, University Hospital of Wales, Cardiff, UK; claire.gallagher2{at}


The porphyrias are rare disorders of haem biosynthesis. Diagnosis requires demonstrating increased porphyrins or porphyrin precursors in blood, urine and faeces. Patients may only be investigated once, and therefore, understanding the preanalytical factors affecting the reliability of results is crucial. Guidance for sample handling exists, but published evidence regarding the stability of porphyrins and their precursors is limited. The aim of this study was to evaluate the effect of light exposure and different storage temperatures on analyte stability for measurement of urinary aminolaevulinic acid and porphobilinogen, total urine porphyrin and plasma porphyrin. Our results confirm that all samples should be protected from light. Results from samples exposed to light for greater than 4 hours should be interpreted with caution and repeat samples requested. If transported to a specialist laboratory, samples should be stored at 4°C before transport. Transit time at ambient temperatures should be less than 24 hours.

  • Chemistry, Clinical
  • Medical Laboratory Science

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  • Handling editor Patrick J Twomey.

  • Contributors CJG, L-AB, RC, MJ and DS-B designed the study protocol, interpreted the data, reviewed the final manuscript. CJG wrote the initial draft, created the figures and tables. DS-B conceived the project idea, coauthor, final edits, response to reviewers. L-AB, RC and MJ performed the analytical work.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.