First-line tests

No single test is effective for screening for all porphyrias. However, one of two tests can be relied upon in almost all situations, depending on the symptoms. Information about screening tests is summarized in Table 2 below.

The symptoms of porphyrias are either due to effects on the nervous system or the skin. Acute porphyrias lead to a variety of effects on the nervous systems such as abdominal pain, nausea, vomiting, pain in the extremities and elsewhere, muscle weakness and altered mental functioning. Cutaneous porphyrias lead to skin manifestations in sun-exposed areas (photosensitivity). These may include chronic blistering or more acute pain and swelling. Some porphyrias have both cutaneous and neurological manifestations.

Acute porphyrias. Measurement of porphobilinogen (PBG) in urine can be relied upon for screening for the acute porphyrias when there are neurological symptoms such as abdominal pain. PBG is markedly increased in almost all patients with symptoms of acute Porphyria and is never markedly increased in diseases other than acute Porphyria. Therefore this test is both sensitive and specific.


If urine ALA, PBG and total porphyrins are normal, it is quite certain that any recent symptoms are not due to an acute Porphyria. If these are markedly increased, further testing is needed. An isolated increase in urine porphyrins (especially coproporphyrin) is nonspecific and therefore does not always require further testing.


If this test is normal, cutaneous porphyrias that cause blistering skin lesions are effectively excluded. Further testing is needed if total plasma porphyrins are increased. But although this is a highly effective screening test, in that it is both sensitive and specific, it is less sensitive than an erythrocyte protoporphyrin determination in detecting EPP.

Table 2. First-line testing for patients in whom porphyria is suspected as a cause of either neurological symptoms or photosensitivity.

Symptoms Most sensitive and specific test for screening when symptoms are present
Neurological (acute abdominal pain, etc.) Urinary delta-aminolevulinic acid and porphobilinogen (a total urinary porphyrin determination is also recommended.)
Skin photosensitivity Total plasma porphyrins