Serum Alanine Transaminase as a Predictor of Type 2 Diabetes Incidence: The Yuport Prospective Cohort Study

Prior studies have shown an association between the incidence of diabetes with liver enzymes, such as alanine transaminase (ALT). Liver fibrosis scores, such as the Fibrosis-4 index which indicates chronic liver damage, were also associated with diabetes development. However, no literature compared predictive accuracy between ALT and Fibrosis-4 index. Thus, we aimed to determine it, and to assess its association using inverse probability of treatment weighting. This was a non-concurrent prospective cohort study of 9,748 subjects without diabetes receiving Yuport Health Checkup in Japan between 1998 and 2006. ALT was categorized into three groups: the highest ALT group (men ≥ 30 U/L and women ≥ 20 U/L), the middle (men ≥ 20 and < 30 U/L, and women ≥ 14 and < 20 U/L), and the lowest (men < 20 U/L and women < 14 U/L). The primary outcome was the new onset of diabetes. The area under the receiver operating characteristic curves (AUC) of ALT for predicting the diabetes development was higher than that of any other markers of liver damage. The AUC for ALT was 0.71, while that for the Fibrosis-4 index was 0.51 (p < 0.001 for the difference between the AUCs). The highest and middle ALT groups had a significantly higher incidence of diabetes than the lowest group: adjusted relative risk 1.79 [95% confidence interval (CI): 1.29, 2.58], and 1.64 [95% CI: 1.17, 2.38] respectively. Of the various indicators of liver function, ALT is likely to be the most accurate and associated predictor of diabetes development.