Laboratory Testing

  • During a suspected porphyria attack, a urinary PBG/ALA test can enable the diagnosis of acute hepatic porphyria (AHP).1
  • The standard method for diagnosis for AHP is measurement of the urinary porphobilinogen, or PBG, using a spot urine sample (i.e., a single-void urine sample) (see figure).2,3
  • In fact, a 24-hour urine collection is not necessary nor recommended.4
  • Urinary biomarkers such as PBG are reported as a ratio to urinary creatinine (UCr) concentration to control for variations in urine flow rate.5
  • Urinary ALA is the first-line test for ADP.1
  • Urine PBG tests can be done in a qualitative or semi-quantitative manner and are accurate and highly specific for acute porphyria.2,3
  • These tests can provide rapid results; routine requests can be assayed within 5 working days and urgent requests should be discussed with the laboratory and can be telephoned or faxed as soon as they are available.4
  • A common error is ordering a urinary porphyrin profile instead of a urinary PBG. Urinary porphyrin profile is a nonspecific test and is one of the most common causes of misdiagnosis in these patients.6,7
    • There is no need for serum or stool test. These other analytes are useful for distinguishing between AIP vs HCP or VP, however, elevation of urinary PBG is all that is needed for a diagnosis of AHP.2,3,6
AHP testing algorithm

 


Herbert L. Bonkovsky, MD - “A current unmet medical need in acute hepatic porphyria (AHP) is that we no longer have available a rapid turnaround quantitative or semi-quantitative test for urinary PBG.10 Even big university medical centers are no longer doing their own urinary PBG testing; they send it out to a reference laboratory, which usually means 3 to 7 days before results are received, and the patient may be discharged from the ER and lost to follow-up.8 Therefore, even a strongly positive elevated PBG may be missed and another chance for early diagnosis is not being made. As gastroenterologists, it is important for us to perform careful patient histories and follow up on recent ER visit lab results, or re-test patients we suspect may have an AHP.”

1. Bissell DM, Wang B. J Clin Transl Hepatol. 2015;3(1):17-26. 2. Cuoghi C, Marcacci M, Ventura P. J Emerg Med Trauma Surg Care. 2015;1:1. 3. Harper P, Sardh E. Expert Opinion on Orphan Drugs. 2014;2(4):349-368. 4. Supra-Regional Assay Service. (SAS): Urinary porphobilinogen (PBG). http://www.sas-centre.org/assays/metabolism/porphyrins/urinary-porphobilinogen-pbg. Accessed April 12, 2018. 5. Waikar SS, Sabbisetti VS, Bonventre JV. Kidney Int. 2010;78(5):486-494. 6. Besur S, Hou W, Schmeltzer P, Bonkovsky HL. Metabolites. 2014;4(4):977-1006. 7. Balwani M. Clin Adv Hematol Oncol. 2016;14(11):858-861. 8. Besur S, Schmeltzer P, Bonkovsky HL. J Emerg Med. 2015;49(3):305-312. 9. Woolf J, Marsden JT, Degg T, et al. Ann Clin Biochem. 2017;54(2):188-198. 10. American Porphyria Foundation. Tests for Porphyria diagnosis.  http://www.porphyriafoundation.com/testing-and-treatment/testing-for-porphyria/tests-for-porphyria-diagnosis. Accessed April 12, 2017.

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