The persistent increase of aspartate aminotransferase (AST) due to the presence of a macro-AST can confuse diagnostic or therapeutic decisions in many clinical situations.In this study, we report a case of isolated and persistent AST-elevation without any clinical sign 2014 dodge ram 1500 fender flares of dysfunction in organs such as the liver, skeletal muscle, cardiac muscle, etc.Despite various investigations, no definite cause for the elevation of read more AST could be found.With the help of polyethylene glycol (PEG) precipitation, we showed that macro-AST formation was responsible 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.