Updated upper limits of normal serum alanine aminotrasferase levels for screening metabolic dysfunction-associated fatty liver disease in obese children

Abstract

Alanine aminotransferase (ALT) is a cost-effective screening test for asymptomatic liver diseases. The aims of this study are to redefine the ULNs of ALT using the 2010-2012 Nutrition and Health Survey in Taiwan (NAHSIT) database and to determine whether the updated ULNs can better screen for metabolic dysfunction-associated fatty liver disease (MAFLD) in obese children. Reference data were obtained from 2895 NAHSIT participants (1442 boys, 1453 girls) aged 6-18 years. Participants with any of MAFLD-related metabolic risk factors, including overweight/obesity, elevated triglyceride, low high-density lipoprotein cholesterol and high fasting glucose, were excluded. This study compared the sensitivities of different ULNs of ALT for detecting MAFLD in our previously established cohort of obese children. The ULNs of ALT defined as the 95th percentile in metabolically healthy NAHSIT participants were 23 IU/L for boys and 18 IU/L for girls. When using the updated ULNs, the percentages of elevated ALT levels were 13.0% in boys and 7.8% in girls of all NAHSIT participants. When using the updated ULNs of ALT to detect MAFLD in obese children, the sensitivity was 84.0% in boys and 74.3% in girls. In contrast, when using the conventional ALT cutoff (>40 IU/L), the sensitivity decreased to 61.4% in boys and 36.4% in girls. After taking into account MAFLD-related metabolic risk factors, the ULNs of ALT are 23 IU/L for boys and 18 IU/L for girls in Taiwan. The updated ULNs may be better cutoffs for screening MAFLD in obese children.