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Macro-aspartate aminotransferase in a female with antibodies to hepatitis C virus


Detlef Ritter, Saint Louis University Hospital, 4th floor DT, 3635, Vista Ave., St. Louis, MO 63110, USA. Tel: 314 577 8694. Fax: 314 268 5645.


Abstract: Persistent elevation of aspartate aminotransferase (AST) activity in serum due to the presence of a macroenzyme form of AST (macro-AST) may lead to diagnostic confusion in many clinical conditions, particularly those associated with chronic liver disease. We describe a case of macro-AST arising in an adult female with a false-positive hepatitis C virus (HCV) RNA test result that was not accompanied by other biochemical or histologic evidence of liver disease. The presence of macro-AST in serum was confirmed utilizing size-exclusion, high performance liquid chromatography (HPLC) and Protein G-agarose beads to precipitate immune complexes of AST and immunoglobulin G followed by centrifugation and AST activity measurements in the supernatant. A brief review of the clinical enzymology of AST and methods used to quantify serum macro-AST activity is provided.