ABSTRACT
Objective To investigate the intralaboratury and interlabomtory variations of measurements for ALT and AST among four domestic reference laboratories. Methods The International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) reference procedures and IFCC procedures without pyridoxal 5-phosphate (PLP) were performed in the reference laboratories. Intralaboratory and interlaboratory CVs were compared with those in 2006 and 2007 IFCC External Quality Assessment Scheme for Reference Laboratories (RELA). Meanwhile, deviations of results for ALT, AST and AST/ALT between two methods were calculated. Results Interlaboratory CVs were generally higher than intralaboratory CVs. Interlaboratory CVs among the 41 laboratories were lower than these in RELA. Results of ALT and AST using method with PLP were higher than those using method without PLP. Difference of AST/ALT ratio between the two methods was significant. Conclusions For reference measurement of the 2 enzymes, interlaboratory CVs of < 3.5 are achievable on frozen serum materials. Measurements on lyophilized materials may have higher CVs. Further studies are needed for the investigation of the differences between results obtained in the absence and presence of PLP.