If acute viral hepatitis is suspected, the following tests 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 hepatitis C virus (anti-HCV) and hepatitis C RNA (HCV-RNA) polymerase chain reaction If any of the hepatitis B tests are positive, further serologic testing may be necessary to differentiate acute from past or chronic infection (see table Hepatitis B Serology).