Upper Reference Limits for Aminotransferase Activities and the Prevalence of Elevated Aminotransferase Activities in a Korean Population

Background: Despite suggestions to lower the upper reference limits (URL) for aminotransferase activities to increase the detection of liver disease, there is no generally accepted URL in the general Korean population. Methods: We set the URL for alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities at the 97.5th percentile in a population at low risk for liver disease (n=3316; negative HBs antigen, low alcohol intake, normal waist circumference, normal lipid or carbohydrate metabolism, and absence of medication use) derived from the 2007 to 2009 Korean National Health and Nutrition Examination Survey (KNHANES; n=16,608). Results: The URLs for ALT activity were 53 IU/L for men and 30 IU/L for women, and the corresponding limits for AST activity were 37 IU/L for men and 29 IU/L for women. The age-adjusted prevalence of the elevated ALT activity was 8.6% [95% confidence interval (CI), 8.2%-9.1%] in the 2007 to 2009 KNHANES and 6.9% (95% CI, 6.3%-7.5%) in the 2001 KNHANES, a relative increase of 24.6% (P<0.05). This increase was concentrated among those aged 20 to 29, with a relative increase of 66.7%, and those aged 30 to 39, with a relative increase of 54.4%. There was no significant change in the prevalence of elevated AST activity. Conclusions: The URL for ALT activity among the general Korean population is clearly higher than recently proposed thresholds. The trajectory of the increasing prevalence of elevated ALT activity heralds an increased burden of chronic liver disease in the future Korean population.