Macro-aspartate aminotransferase in a female with antibodies to hepatitis C virus.
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.
Collins
John
J
Departments of Pathology and Laboratory Medicine, Saint Louis University School of Medicine, St Louis, MO 63110, USA.
Ritter
Detlef
D
Bacon
Bruce R
BR
Landt
Michael
M
Creer
Michael H
MH
D000328:Adult; D001219:Aspartate Aminotransferases / Q000097:blood*; D002851:Chromatography, High Pressure Liquid; D004796:Clinical Enzyme Tests; D005260:Female; D018937:Hepatitis C Antibodies / Q000097:blood*; D006801:Humans; D008107:Liver Diseases / Q000175:diagnosis*; D012367:RNA, Viral / Q000097:blood
D018937:Hepatitis C Antibodies; D012367:RNA, Viral; D001219:Aspartate Aminotransferases