The persistent increase of aspartate aminotransferase (AST) due to the presence of a macro-AST can confuse diagnostic BOTTOMS or therapeutic decisions in many clinical situations.In this study, we report a case of isolated and persistent AST-elevation without any clinical sign of dysfunction in organs such as the liver, skeletal muscle, cardiac muscle, etc.Despite various investigations, no definite cause for the elevation of AST could be found.With the help of polyethylene glycol (PEG) precipitation, we showed that macro-AST formation was responsible 5 Piece Full Platform Bedroom for the elevation of the AST titer in this case.Early recognition of macro-AST by PEG precipitation can prevent diagnostic confusion and unnecessary and even invasive tests.