GPT and hepatitis C virus infection: In particular, the SNP at nucleotide -443 (C or T) showed an association with the activity of hepatitis C. This activity was defined as the serum levels of alanine aminotransferase (ALT): low (ALT > 30 IU/L), medium (30 < ALT < 80 IU/L), or high (ALT > 80 IU/L).