Dear Editor, we read the recent publication on “Upper Limit of Normal for Serum Alanine Transaminase (ALT)” with a great interest. Mohen et al. [1] reported that “The mean ALT in men and women were 21.87 ± 2.9 (97.5th percentile 28 U/L) and 19.35 ± 3.3 (97.5th percentile 24 U/L) respectively.” and concluded that “There is a need to re-consider ALT levels in our population for better detection of individuals at risk for liver disease [1].” We would like to share ideas and experience on this topic. First, the healthy population in this study might not a disease free population. The statistical confirmation for the normal distribution of the ALT results is required for setting any normal reference value. In our experience from Thailand, where there is a high rate of silent hepatitis virus infection, the reference value derived from the study of healthy people, without screening for hepatitis B carrier, is high [2]. If the reference value is intended for using for detection of individual risk for liver disease, exclusion of the case with underlying silent hepatitis carrier status is needed.