The change of alanine aminotransferase distributions among US youths, NHANES 1988–2020

Objectives: The trend of alanine aminotransferase (ALT), a biomarker of metabolic dysfunction-associated steatotic liver disease (MASLD, formerly known as nonalcoholic fatty liver disease), remains poorly described for the pediatric population because no widely accepted cutoffs are available to categorize ALT value. We described the nuanced changes in the distribution of ALT continuous values. Study Design: We analyzed the data from 15,702 adolescents aged 12–19 who participated in the National Health and Nutrition Examination Surveys between 1988 and 2020. The ALT distributions were standardized for age and sex. The prevalence of elevated ALT was also assessed. Results: The ALT geometric mean increased from 11.82 U/L in 1988–1994 to 17.24 U/L in 1999–2004, stayed above 17 U/L for a decade, and then decreased to 14.04 U/L in 2017–2020 (p for the quadratic trend <0.001). However, the 95^th percentile of the ALT distribution remained above 35 U/L by the end of the study period after jumping from 26.02 U/L in 1988–1994 to 33.83 U/L in 1999–2004. The prevalence of elevated ALT (>42 U/L in boys and 30 U/L in girls), doubled from 1.53% (0.87%–2.19%) in 1988–1994 to 3.49% (2.73%–4.25%) in 1999–2004, and lingered around 4% through 2020. Conclusions: The ALT mean decreased in recent years, but the prevalence of elevated ALT remained persistently high. Population-wide reductions in fructose consumption may have contributed to the decrease in ALT mean. The stagnant right end of the distribution, manifesting as the high prevalence of elevated ALT, calls for intensified clinical prevention.