Interpretation
Raised faecal porphyrins may indicate an underlying porphyria, although may be secondary to bacterial contamination of the stool or haemorrhage into the GI tract.
If raised, HPLC profiling will usually be added for metabolite profiling which will give an indication of underlying porphyria and which type.
For example, faecal iso-coproporphyrin is regarded as a hallmark of porphyria cutanea tarda (PCT).
Faecal CIII:CI ratio is elevated in hereditary copro-porphyria (HCP).
Urine and blood porphyrins often provide useful adjunctive diagnostic information.
Note that a raised urine PBG is the diagnostic hallmark of an acute attack of porphyria.
A negative urine PBG during an acute symptomatic episode excludes acute porphyria as the cause.
Of the acute porphyrias (AIP, VP, HCP), faecal porphyrins are not raised in AIP.
Test Method
Extraction, Spectrophotometric scan
