[Isolated increase of the serum aspartate aminotransferase level in a young asymptomatic patient: macro-AST].

A 23-year-old asymptomatic patient wanted to become pregnant and had a blood analysis done at her general practitioner's office. The serum aspartate aminotransferase (AST) level was unexpectedly elevated: 139 U/l (reference value: < 32). The values for the other liver enzymes were normal. Extensive biochemical and imaging studies revealed no other abnormalities. The presence of so-called macro-AST was suspected. In this condition, AST forms complexes with other proteins, primarily IgG, which leads to an increased serum level. This has no clinical consequences. The presence of such complexes was confirmed by means ofa polyethylene glycol precipitation assay. This is a simple test for the detection of macro-AST, which saves the asymptomatic patient further invasive diagnostic procedures.