The population distributions, upper normal limits and correlations between liver tests among Australian adolescents
AIM: Relatively little is known about the results of liver tests among adolescents. The purpose of this study was to describe the distributions of liver tests, to identify the upper normal limits (UNLs) and to describe the correlations among liver tests. METHODS: Overnight fasting blood samples were collected from a representative population sample of 500 Grade 10 students (15 years old) attending schools in Sydney, Australia. Weight, height and waist girth were measured. UNLs were calculated for each enzyme as the 95th percentiles of the healthy body mass index category, after excluding those with high blood pressure, elevated low-density lipoprotein cholesterol (>or=3.4 mmol/L) or triglyceride concentration (>or=2.25 mmol/L) (n = 246). The distributions of alanine aminotransferase (ALT), gamma-glutamyltransferase (GGT), aspartate aminotransferase (AST) and alkaline phosphatase (ALP) were described, UNLs were identified and the correlations between enzyme concentrations were described. RESULTS: The UNLs for ALT were 32 and 20 U/L; for GGT, 24 and 19 U/L; for AST, 33 and 26 U/L; and for ALP, 385 and 183 U/L, for boys and girls, respectively. ALT concentration was strongly correlated with GGT and AST (r = 0.5-0.6). Neither ALT nor GGT concentrations were correlated with ALP concentration, but AST concentration was moderately correlated with ALP concentration. CONCLUSIONS: These data are valuable in defining the distributions of liver tests, normal liver test ranges and relationships between liver tests among adolescents.