If acute viral hepatitis is suspected, the following tests are done to screen for hepatitis viruses A, B, and C: IgM antibody to hepatitis A virus (IgM anti-HAV) Hepatitis B surface antigen (HBsAg) IgM antibody to hepatitis B core (IgM anti-HBc) Antibody to HCV (anti-HCV) and HCV RNA If the anti-HCV test is positive, HCV RNA is measured to distinguish active from past hepatitis C infection (see table Hepatitis C Serology).