Moreover, the current upper limit of normal for many of the liver enzymes (for example ALT) may be too high, which is probably a consequence of patients with occult NAFLD being included in the generation of normal serum ALT ranges.22 This is perhaps best appreciated in patients with chronic hepatitis B, where treatment guidelines recommend an ALT of >30 U/L as being significant in males and >19 U/L significant for females. This evidence concerns the gene GPT and chronic hepatitis B virus infection.