The Hepatitis Delta / Ab, Total test is performed to detect total antibodies against the Hepatitis Delta Virus (HDV) in the blood. HDV is a virus that causes hepatitis and can only exist and replicate in the presence of the Hepatitis B Virus (HBV), as HDV requires HBV as a "vector" for infection. HDV can increase the severity of hepatitis B, leading to chronic hepatitis, cirrhosis, or even liver cancer.