Porphyrins red cell

Specimen:

5 mL blood in heparinised tube, protected from light and transported rapidly to the laboratory.

Method:

Spectrophotometry or fluorometry.

Reference Interval:

< 900 nmol/L red cells.

Application:

Detection of congenital erythropoietic porphyria (EP) and protoporphyria (PP) in childhood. The test is indicated in some adults with skin photosensitivity not due to porphyria variegata or porphyria cutanea tarda, if mild EP or PP require exclusion.

Interpretation:

Erythrocyte protoporphyrin is raised in PP. It is also raised in lead exposure and may be useful in the assessment of lead intoxication. It is slightly elevated in iron deficiency and anaemia of chronic disease, but should not be used for the diagnosis of these conditions.

Reference:

Braun J. Erythrocyte zinc protoporphyrin. Kidney Int Suppl. 1999 Mar;69:S57-60. Review.