Hepatitis D superinfection
D. Order testing for hepatitis delta virus (HDV) IgM and IgG antibodies and, if positive, test for HDV RNA
The key to the correct diagnosis is recognition that the most likely cause of sudden-onset jaundice and newly elevated aminotransferase and bilirubin levels in a patient with intravenous drug use and chronic HBV infection without acute hepatitis A or C virus infection is HDV. Choice A is incorrect because HIV does not typically cause this level of aminotransferase and bilirubin elevation. Hepatitis E (choice B) is unlikely because the patient has never traveled outside the US and has not eaten raw meat. Anti–smooth muscle antibody testing (choice C) is helpful to diagnose autoimmune hepatitis, but this is not the most likely diagnosis in a patient with chronic HBV infection and intravenous drug use.