<prompt> Infection with hepatitis D virus HDV; delta agent can occur simultaneously with infection with hepatitis B virus HBV or in a carrier of hepatitis B virus because HDV is a defective virus that requires HBV for its replicative function. What serologic test can be used to determine whether a patient with HDV is an HBV carrier?image_questionimage_questionimage_questionimage_question  <response>: In a chronic HBV carrier, there would be no HB core IgM antibody, whereas it would be present in a new HBV infection. The HBe antigen could be present in either an HBV carrier or in acute infection. HBsAg would be present in either a new infection or in the carrier state, while HBsAb would not be present in either case. Reference: Ananthanarayan and Paniker;s Textbook of Microbiology Tenth edition 