A street person well known to the local public health clinic appears to have acute symptoms of hepatitis and tests positive for HDV antigen. Knowing that HDV requires HBV, which of the following sets of test results shows this patient had chronic HBV infection and was superinfected with HDV?
A street person well known to the local public health clinic appears to have acute symptoms of hepatitis and tests positive for HDV antigen. Knowing that HDV requires HBV, which of the following sets of test results shows this patient had chronic HBV infection and was superinfected with HDV?
💡 Explanation
## **Core Concept**
The question revolves around the serological diagnosis of hepatitis B virus (HBV) and hepatitis D virus (HDV) infections. HDV is a satellite virus that requires the envelope proteins of HBV to replicate. Therefore, HDV infection can only occur in individuals who are either currently infected with HBV or have a history of HBV infection.
## **Why the Correct Answer is Right**
To determine that a patient had chronic HBV infection and was superinfected with HDV, we need to look for serological markers indicating long-standing HBV infection and acute HDV infection. Chronic HBV infection is characterized by the presence of **HBsAg (hepatitis B surface antigen)** for more than 6 months, **HBeAg (hepatitis B e-antigen)**, and/or **anti-HBe (antibody to hepatitis B e-antigen)** with **HBV DNA** positivity. Superinfection with HDV in a chronic HBV carrier is marked by the presence of **anti-HDV IgM (immunoglobulin M antibody to hepatitis D virus)**.
## **Why Each Wrong Option is Incorrect**
- **Option A:** This option shows HBsAg negative and anti-HBs positive with anti-HDV IgM positive. The presence of anti-HBs (antibody to hepatitis B surface antigen) indicates immunity to HBV, either through vaccination or past infection. The anti-HDV IgM positivity suggests acute HDV infection, but the absence of HBsAg rules out current HBV infection.
- **Option B:** This option indicates acute HBV infection (HBsAg, anti-HBc IgM positive) and acute HDV infection (anti-HDV IgM positive). It does not indicate chronic HBV infection.
- **Option C:** This option shows HBsAg positive, anti-HBc IgG positive (indicative of chronic or past HBV infection), and anti-HDV IgG positive (indicative of past HDV infection). The absence of anti-HDV IgM makes acute HDV superinfection less likely.
- **Option D:** This option shows HBsAg positive (chronic HBV infection), anti-HBc IgG positive, and anti-HDV IgM positive. The presence of anti-HDV IgM specifically indicates acute HDV infection.
## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that HDV infection can only occur in the presence of HBV. Therefore, a patient with HDV infection must either be a chronic HBV carrier or have acute HBV infection. Superinfection of HDV in a chronic HBV carrier often leads to more severe liver disease.