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The porphyrias are a group of rare, mostly inherited metabolic disorders in the haem biosynthetic pathway. Recommended best methodological practice for general clinical laboratories initial testing for porphyria and algorithm for onward referral to specialist porphyria laboratories are available from the British and Irish porphyria network. https://bipnet.org/bipnet-laboratory-practice/
Investigation for cutaneous porphyria:
Investigation for latent porphyria or family history:
Contact a specialist porphyria laboratory for advice. Clinical, family details are usually required.
The programme provides an assessment of the analytical performance of first-line laboratories undertaking both qualitative and quantitative analysis of PBG and TUP for the investigation of an acute attack and for laboratories offering an expanded repertoire for the investigation of cutaneous porphyria which also includes EDTA plasma and faecal porphyrin.
Six urine samples are distributed every 3 months, 3 each for PBG and TUP along with 3 EDTA plasma samples for plasma porphyrin. Interpretative cases are distributed twice a year with Faecal porphyrin samples dispatched annually. For this programme participants are allowed 3 weeks to return their results.
Reference target value assignment, EDTA plasma patient samples, faecal samples and clinical case interpretation are kindly provided by the Cardiff Porphyria Service.
The Programme assesses both laboratory and method performance, including bias and within batch imprecision. The programme also assesses the laboratory’s pre and post analytical phases through the distribution of challenging samples (too dilute or concentrated) and the interpretation of Clinical cases.
|Analyte||Approx. Range Covered|
|Porphobilinogen (PBG)||0 - 170||mmol/L|
|PBG / Creatinine Ratio||0 - >30||mmol/mmol|
|Total Urine Porphyrin (TUP)||0 - 4000||nmol/L|
|TUP / Creatinine Ratio||0 - >500||nmol/mmol|
|Plasma Porphyrin||8 - 300||nmol/L|
|Faecal Porphyrin||35 - 700||nmol/g|
|Clinical case interpretation|