A patient is found to be positive only for Anti HBsAg. All other viral markers are negative.The likely diagnosis is :
**Core Concept**
The patient's positive result for Anti-HBsAg indicates the presence of antibodies against the hepatitis B surface antigen (HBsAg). This suggests that the patient has been previously exposed to hepatitis B virus (HBV) and has developed immunity. However, the absence of other viral markers such as HBsAg, HBeAg, and HBV DNA suggests that the patient is not actively infected.
**Why the Correct Answer is Right**
The presence of Anti-HBsAg indicates that the patient has mounted an immune response against HBV, likely due to either vaccination or past infection. The absence of HBsAg and HBeAg suggests that the virus is not actively replicating in the liver. Additionally, the absence of HBV DNA further supports the notion that the patient is not actively infected. The presence of Anti-HBsAg suggests that the patient has developed immunity, which is a key concept in understanding the patient's clinical status.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is not provided.
**Option B:** This option is not provided.
**Option C:** This option is not provided.
**Option D:** This option is not provided.
**Clinical Pearl / High-Yield Fact**
It's essential to note that the presence of Anti-HBsAg in the absence of other viral markers is a key indicator of immunity to HBV. This is particularly important in clinical settings where patients may be required to undergo screening for HBV before undergoing certain medical procedures.
**Correct Answer:** C. Immune status following HBV vaccination or past infection.