Development and evaluation of percentile curves of serum alanine aminotransferase in older adults: A multi-cohort study.

Objective: Age independently impacts alanine aminotransferase (ALT) levels. This study was conducted to develop age- and sex-specific ALT percentile curves among older adults and evaluate their diagnostic performance across two external cohorts.

Methods: We developed ALT percentile curves using data from a reference population aged 50-90 years (n = 20,039). We evaluated diagnostic performance of various ALT thresholds (40 U/L, American College of Gastroenterology [ACG]'s 33 U/L [men] and 25 U/L [women], and the new percentile curves) for infections of hepatitis B virus and hepatitis C virus, metabolic dysfunction associated steatotic liver disease, and excessive alcohol consumption in two external cohorts.

Results: ALT percentile curves declined with age. In men, the 95th percentile decreased from 31.4 U/L at 50 years to 21.7 U/L at 90 years; in women, from 26.1 U/L to 17.8 U/L. The 95th percentile curves achieved the highest Youden's index and area under the receiver operating characteristic (AUROC) across the three thresholds in two external validation cohorts, with the Youden's index and AUROC of 0.141 and 0.571 (95% CI: 0.555-0.586) in external cohort 1, and 0.435 and 0.717 (95% CI: 0.680-0.754) in external cohort 2, respectively.

Conclusions: The newly proposed ALT percentile curves may serve as a valuable reference for screening liver diseases in older adults.