An HIV infected individual will show a negative result for an antibody-antigen based test if the body has not produced antibodies. For such a situation, which of the following test could be used to confirm the presence of HIV?

Options

A. MRI
B. PCR
C. ELISA
D. Widal test

Answer

To solve the question regarding which test could confirm the presence of HIV in an individual who shows a negative result for an antibody-antigen based test, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Context**: The question states that an HIV-infected individual shows a negative result for an antibody-antigen based test. This typically means that the body has not yet produced antibodies against HIV, which can occur in the early stages of infection.

2. **Identify the Tests Listed**: The options provided are:
- MRI
- PCR
- ELISA
- Vidal test

3. **Analyze Each Test**:
- **MRI**: This is an imaging test used to visualize internal organs and tissues. It does not detect infections or antibodies, so it is not relevant for confirming HIV.
- **PCR (Polymerase Chain Reaction)**: This test detects the genetic material of the virus (HIV RNA or DNA) rather than antibodies. It can identify HIV even when the antibody levels are low or undetectable, making it suitable for early detection.
- **ELISA (Enzyme-Linked Immunosorbent Assay)**: This is an antibody-based test. Since the question states that antibodies have not been produced, this test would yield a negative result.
- **Vidal Test**: Similar to ELISA, this test is also based on detecting antibodies and would not be effective in this scenario.

4. **Conclusion**: The only test among the options that can confirm the presence of HIV in the absence of antibodies is the PCR test. It can detect the virus's genetic material directly.

### Final Answer:
The correct answer is **PCR**.

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