Clinical suspicion of acute porphyria.
May include otherwise unexplained abdominal pain, neurological or psychotic features, skin lesions.
Quantitation of PBG is usually added by the laboratory when urine porphobilinogen (PBG) screen is positive.
It should be noted that borderline positive screens may result from a concentrated urine.
PBG quantitation makes allowance for the degree of urine concentration.
In some cases, it may be an appropriate test for latent acute intermittent porphyria (AIP).
Urine protect from light, to Trace metals fridge.
Random urine, protect from light.
If overnight - Frozen
Protect from light.
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.
For raised urine PBG, the differential diagnosis is acute intermittent porphyria (AIP), variegate porphyria (VP) or hereditary coproporphyria (HCP).
Definitive characterisation requires a full set of samples – blood, urine and faeces protected from the light for porphyrin quantitation and further studies, including HPLC profiling, fluorescence scanning and genotyping as appropriate.
Normal urine PBG does not exclude a non-acute porphyria such as porphyria cutanea tarda (PCT) or erythropoietic protoporphyria (EPP). For evaluation of these disorders a full set of samples – blood, urine and faeces protected from light is required.
< 1.5 umol/mmol crn
Contact Canterbury Health Laboratories on +64 3 364 0484 or email LabInfo@cdhb.health.nz
Test performed in conjunction with ALA.
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