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Medline ® Abstract for Reference 25

of 'Approach to the patient with abnormal liver biochemical and function tests'

Macroenzyme as a cause of unexplained elevation of aspartate aminotransferase.
Litin SC, O'Brien JF, Pruett S, Forsman RW, Burritt MF, Bartholomew LG, Baldus WP
Mayo Clin Proc. 1987;62(8):681.
Aspartate aminotransferase (AST) can exist as a macroenzyme by forming a complex with an immunoglobulin. This immunoglobulin-complexed macromolecule can cause an elevation in serum AST activity, which may be detected on routine blood chemistry analysis and erroneously considered to indicate the presence of liver disease. Clinicians should be aware of this phenomenon so patients are not subjected to unnecessary procedures. In patients with unexplained AST elevation, liver and muscle disease can be biochemically excluded by the finding of normal serum levels of alanine aminotransferase and creatine kinase. The presence of macro-AST can be determined by exclusion chromatography, electrophoresis, and activation assays with pyridoxal 5-phosphate. The elevated AST values can persist for many years.