Study of serum argininosuccinate lyase determination for diagnosis of liver diseases

The objectives of this research were to establish an automatic analysis method for the determination of serum argininosuccinate lyase (ASL) and to investigate the value of serum ASL test in the diagnosis of various liver disorders. According to the chemical reaction catalyzed by ASL, an enzyme-coupled reaction system was designed, and a methodology evaluation of this method was performed. A total of 291 patients with various liver diseases, 247 patients with nonliver disease and 32 healthy controls, were recruited, their serum levels of ASL and traditional hepatopathy markers, including alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyltransferase (GGT), lactate dehydrogenase (LDH), alkaline phosphatase (ALP), and total bilirubin (TBil), were all determined, and their diagnostic values in liver diseases were analyzed and compared. Liver biopsy and the score of histopathological inflammation grading were performed in 31 patients with hepatopathy to explore the correlation between serum ASL level and hepatic histopathological change. A continuous monitoring assay method of serum ASL activity was established, which could be performed with automatic biochemistry analyzer. Methodological evaluation exhibited that the precision of this method was good indicated by the 4.0% intraassay coefficient of variation (CV), and 5.9% interassay CV. The mean recovery was 100.5%, linear range was from 0 to 167.7 U/L, and the lowest detection limit was approximately 0 U/L. All of the tested hepatopathy markers listed above were significantly increased in the liver disease group. However, levels of traditional markers of hepatopathy were all significantly increased at different degrees (all P<0.001) in patients with nonliver diseases; in contrast, there were no significantly increased ASL levels in all non-hepatopathy groups (P=0.335). The receiver operating characteristic (ROC) curve showed that the sensitivity and specificity of ASL were 100% and 91.1% (cutoff value=8 U/L), respectively, in the assessment of liver diseases. In contrast, ALT levels were 97.6% and 24.7%, and AST levels were 83.8% and 28.3% (both cutoff values=40.0 U/L), respectively. A positive correlation (r=0.417, P=0.019) was observed between serum ASL levels (86.9+/-26.5) and scores of histopathological inflammation grading (SHIG) (9.83+/-3.36). The sensitivity and specificity of ALS is much higher than that of ALT and AST for the diagnosis of liver diseases. ASL may be a more valuable marker for estimating hepatopathy.