ALT = alanine aminotransferase; anti-HCV = antibody to hepatitis C virus; AST = aspartate aminotransferase; HBsAg = hepatitis B surface antigen; IgM anti-HAV = IgM antibody to hepatitis A virus. Serology In patients with findings suggesting acute viral hepatitis, the following studies are done to screen for hepatitis viruses A, B, and C: IgM antibody to HAV (IgM anti-HAV) Hepatitis B surface antigen (HBsAg) IgM antibody to hepatitis B core (IgM anti-HBc) Antibody to HCV (anti-HCV) Hepatitis C RNA (HCV-RNA) polymerase chain reaction If any are positive, further serologic testing may be necessary to differentiate acute from past or chronic infection (see tables Hepatitis A Serology, Hepatitis B Serology, and Hepatitis C Serology).