Diagnostic Criteria and Clinical Implications for Acute Hepatic Porphyria

Diagnostic Criteria

During an acute porphyria attack, PBG levels are significantly elevated, typically at least 5-fold above the upper limit of normal, according to the American Gastroenterological Association 1, 2
The European Association for the Study of the Liver suggests that the PBG/creatinine ratio is typically increased to more than 10 times the upper limit of normal during an active attack 3
A normal PBG level in a symptomatic patient effectively rules out acute porphyria as the cause of symptoms, with the rare exception of ALAD deficiency porphyria, as stated by the European Association for the Study of the Liver 3

The American Gastroenterological Association recommends that a PBG level at the upper limit of normal during ongoing symptoms is not consistent with an acute porphyria attack 1, 3
The patient's symptoms are most likely due to another cause and further investigation for alternative diagnoses is warranted, according to the American Gastroenterological Association 5
If clinical suspicion for porphyria remains, the American Gastroenterological Association suggests considering measuring both ALA and PBG during a more severe symptomatic episode 4
The European Association for the Study of the Liver notes that the only exception to the rule of normal ALA and PBG levels ruling out AHP is the extremely rare autosomal recessive ALAD deficiency porphyria, where PBG is typically normal but ALA is significantly increased 3