Diagnosis of Erythropoietic protoporphyria (EPP)
1. Total erythrocyte porphyrin concentration is increased in erythropoietic protoporphyria, congenital erythropoietic porphyria, rare homozygous variants of the autosomal dominant porphyrias, iron deficiency, haemolytic anaemia and lead poisoning.
2. Only in EPP and rarely in sideroblastic anaemia, is free protoporphyrin increased and to a much greater extent than zinc protoporphyrin.
3. This assay is not recommended for the investigation of lead poisoning. The assay of choice for this is blood lead.
5-10ml of fresh EDTA anti-coagulated blood. Blood porphyrin levels decrease rapidly on exposure to light (the half life is 24hrs).
The minimum volume required for assay is 5ml – allowing for both screening and quantitation if necessary. Paediatric investigations should be discussed with the laboratory.
Dispatch samples by first class post in a container that conforms to Post Office regulations, protected from light, to arrive in the laboratory with 24-48 hours of sampling. When a delay in dispatch is anticipated, due to weekend or bank holiday, samples should be stored at 0-40C and protected from light.
DO NOT FREEZE OR SEPARATE.
Routine requests are assayed within 5 working days after receipt of sample. Urgent requests should be dispatched via a courier service. Results can be telephoned or faxed as soon as they become available.
Total erythrocyte protoporphyrin = 0.5-1.7 umol/L (Cardiff)
Free erythrocyte protoporphyrin = 0-200 nmol/l cells (King’s)
Zinc erythrocyte protoporphyrin = 0-800 nmol/l cells (King’s)
Centre offering this assay
Cardiff UHW Porphyria Diagnostic Service
Frontline tests for the investigation of suspected porphyria. A. C. Deacon & G. H. Elder. J. Clin. Pathol. 2001; 54:500-507