Tag Archives: macro AST

Blog Case Report: A Persistent Elevated AST in Teen with IBD and ADHD

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A recent case reminded me of the quote by Helena Ravenclaw in Harry Potter: “”If you have to ask, you’ll never know. If you know, you need only ask.”

One of my colleagues recently diagnosed a teenage boy with ulcerative colitis. His past medical history was notable for ADHD. At the time of his evaluation, he was noted to have an elevated AST.

Labs:

  • June: AST 143, ALT 8, Hepatitis B immune
  • August: AST 190, ALT 10, Albumin 4.7, T protein 7.3, T bili 0.4, D bili 0.1, Alk phos 168; GGT 10, CPK 93

The concern at the time was whether his elevated AST should preclude using his ADHD medicine and whether there was an underlying liver disease. Based on the pattern of liver enzyme abnormalities, it was suspected that the patient had macro AST. A blood test was sent to the Mayo clinic and confirmed this diagnosis:

“”The sample was investigated for the presence of macro AST by polyethylene glycol (PEG) precipitation. Serum AST activity = 316 U/L. The AST result post-PEG precipitation = 22 U/L. The results obtained are positive for the presence of macro AST (93% of activity precipitated with PEG). Based on validation studies performed at the Mayo Clinic, a cut-off of >80% AST activity precipitated by PEG indicates the presence of macro AST.” This test is rarely ordered at the Mayo Clinic and is ordered as a miscellaneous test; it is not on the Mayo Clinic’s regular test menu.

Internet description of macro AST: Macro-aspartate aminotransferase (macro AST) is a rare, benign condition that causes a persistent elevation of aspartate aminotransferase (AST) levels in the blood. It’s caused by the binding of AST to immunoglobulins, which results in a high molecular weight macroenzyme that’s excreted from the serum more slowly than normal.

My take: Macro AST diagnosis is useful –it helps eliminate the concern for other conditions. Since it is quite uncommon, it is easier to think of this problem once you have seen it before.

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