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Upper normal threshold of serum alanine aminotransferase in identifying individuals at risk for chronic liver disease



Geum-Youn Gwak, MD, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Irwon-dong, Gangnam-Gu, 135-710, Seoul, South Korea

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Serum alanine aminotransferase (ALT) is an easily available, low-cost screening tool for detecting silent chronic liver disease. Recent studies have suggested that the currently accepted healthy ALT thresholds be lowered.


In this retrospective cross-sectional study, we determined upper thresholds for ALT values in a nationally representative healthy cohort (n = 3337) from the Fourth Korea National Health and Nutrition Examination Survey (KNHANES IV). Sensitivity and specificity of the currently used ALT threshold (40 IU/L, regardless of gender) was compared against study-derived, gender-specific ALT thresholds for detecting individuals at risk for chronic liver disease in 27 913 health check-up participants.


The 95th percentile levels for ALT in healthy weight, metabolically normal, liver disease-free KNHANES participants were 34 IU/L for men and 25 IU/L for women. The prevalence of ALT elevation among health check-up participants was 11.0% in currently used thresholds, and increased to 22.6% with study-derived, gender-specific thresholds. Of the population who were additionally defined to have elevated ALT levels under new ALT threshold, 65.7% were at risk for chronic liver disease. Sensitivity for detecting individuals at risk for chronic liver disease improved from 18 to 33% with new thresholds whereas a trade-off in specificity (from 96 to 88%) was observed.


It is recommendable to lower the current ALT thresholds to better identify individuals at risk for chronic liver disease.