Objectives: Serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) are 2 commonly ordered liver function tests, and ALT has long been considered more liver-specific than AST. Between the 2, the one which is better in predicting liver or non-liver-related mortality remains unsettled.
Methods: The cohort, 416,122 adults, came from a self-paying comprehensive health surveillance program during 1994-2008 and was followed up till 2008. Mortality came from National Death Index, with 10,412 deaths identified. Hazard ratios (HRs), computed by Cox model, and life expectancy, by life table method, were presented for 5 levels of AST and ALT with elevated AST or ALT defined as ≥40 IU/L. Liver disease included liver cancer and other liver conditions.
Results: There were 3 times more elevated ALT (15.4%) than AST (5.7%). However, those with elevated AST had higher mortality for all-cause (HR = 2.44), for liver disease (HR = 27.2), and for liver cancer (HR = 47.6) than its ALT counterparts (HR = 1.69, 10.8, and 20.2, respectively). Elevated AST also lost more years of life expectancy (10.2) than those lost by ALT (5.2) and larger than most common risks. Elevated AST had increased mortality from all cancers (HR = 3.57), stroke (HR = 1.36), respiratory diseases (HR = 1.34), and injuries (HR = 1.82), other than just liver disease. All-cause mortality remained significantly increased, when high risk groups were excluded, such as frequent drinkers, hepatitis carriers, those died from nonmedical conditions, those died in the first 3 years, or advanced fibrosis index based on 4 factors or aspartate transaminase-to-platelet ratio index. Results were consistent between those returned for second visits and those analyzed in initial visits.
Discussion: Those with elevated AST (≥40 IU/L) had life expectancy cut short by 10.2 years, doubled the number of years lost with elevated ALT. For all-cause and for liver-related mortality, AST was an important predictor, better than ALT.