The population prevalence of adverse concentrations and associations with adiposity of liver tests among Australian adolescents

Aim: Paediatric overweight has a high incidence and has serious consequences for health, including non-alcoholic fatty liver disease (NAFLD). However, very little is known about NAFLD among young people, particularly from a population perspective. This paper reports the prevalence of elevated concentrations of four liver enzymes and their associations with adiposity in a representative population sample of Australian adolescents. 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, between February and May, 2004. Weight, height and waist girth were measured. The prevalence of adverse concentrations of the enzymes alanine aminotransferase (ALT), gamma-glutamyltransferase (GGT), aspartate aminotransferase (AST) and alkaline phosphatase (ALP) were described for all boys and girls and by body mass index (BMI) categories. The nature of the associations between the enzyme concentrations and indices of adiposity were characterised, and regression equations for estimating enzyme concentrations from BMI were prepared. Results: The prevalence of adverse concentrations of ALT (most likely as a result of NAFLD) and GGT were approximately 10%, while the prevalence of adverse concentrations of AST and ALP were approximately 7% and 5% respectively. The prevalence of adverse concentrations of ALT, GGT and AST increased across BMI categories, while the prevalence of adverse concentrations of ALP declined across BMI categories. Conclusions: The high prevalence of NAFLD in a population sample of healthy Australian adolescents represents a significant burden of disease.