Evaluation of commercially formulated aspartate aminotransferase and alanine aminotransferase activity determinations by the Scandinavian Committee on Enzymes and IFCC methods as modified for use with automated enzyme analysers.

The performance characteristics of the Scandinavian Committee on Enzymes (SCE) methods for the assay of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were determined using six automated enzyme analysers. The reagent formulation did not include pyridoxal phosphate (PLP). An optimal operating mode was defined for each instrument and precision was assessed in greater detail on four instruments. A points rating system was devised to place the instruments in the following order of proficiency: IL Multistat III, LKB-8600, Gilford 3500, ABA 100. In contrast to AST, the ALT activity of patient samples was unstable at -20 degrees C over periods as short as seven days. The performance characteristics of the IFCC methods for assay of AST and ALT activities were determined by using three automated enzyme analyzers in order to assess the effect of PLP upon precision and activity of four quality control sera, and to compare the SCE and IFCC methods. Precision of AST assays did not alter on omission of PLP from the IFCC formulation, while that of ALT assays showed slight deterioration. The decrease in activity on omitting PLP was variable with each instrument. A points-rating system was devised to place the methods in the following order of precision: AST: IFCC (-PLP) 118, IFCC 109, SCE 61; ALT: IFCC 125, IFCC (-PLP) 97, SCE 66. The IFCC methods offer better precision, and the overall change on omitting PLP is minimal.