Comparison of AST activity measured by a variety of methods and the proposal for commutation to the result of IFCC recommended method on AST

Objectives:To study the relationship of serum AST activity with calibrators or reference materials determined by different methods, and the calculated formula to commute the value of routine methods to the one of IFCC. Methods:Eight different methods for AST determination were compared by assaying human serum samples ( n =87) covering a wide range of AST values. Intermethod comparison between each method and the reference method (method H, without PLP) and commutability of two calibrators (c.f.a.s, Randox) and one reference material (ERM) with human serum specimens were calculated by regression analysis. Results:Methods comparison showed homogeneous results, all the correlation coefficients were close to 1.0 and the intercepts were close to 0. The intermethod behavior of ERM was commutable with the human serum specimens, but the commutability of the two calibrators were not so good. Conclusions:Enzyme reference materials could reduce the deviation of AST values measured by various methods, and became a useful new path of standardization.