Question

Which of the following is the best technique for detecting HIV:

• A. Widal test
• B. Real-time PCR
• C. Polymerase chain reaction
• D. Reverse transcriptase-PCR

Answer 1

The Correct Option is D

The correct option is (D): Reverse transcriptase-PCR.

Answer 2

This question asks which laboratory method works best for picking up HIV infection, given that HIV is a virus whose genetic material is RNA. Let's weigh each option:

1. Widal test: The Widal test detects antibodies against Salmonella typhi, the bacteria that cause typhoid fever. It has no connection to HIV and cannot detect this virus.
2. Real-time PCR: Real-time PCR can quantify DNA and is used in many viral load tests, but on its own it is designed for DNA templates. HIV's genome is RNA, so a plain PCR step cannot directly amplify it without first converting the RNA into DNA.
3. Polymerase chain reaction: Standard PCR amplifies existing DNA sequences. Since HIV carries its genetic code as RNA, not DNA, a basic PCR reaction cannot use the viral genome as a starting template.
4. Reverse transcriptase-PCR: RT-PCR adds a reverse transcriptase step that first converts the viral RNA into complementary DNA, which can then be amplified and detected. Because HIV is a retrovirus that stores its genome as RNA, this conversion step is exactly what is needed to detect and quantify it accurately, including during the early window period before antibodies appear.

Since HIV's genetic material is RNA rather than DNA, only a technique that first transcribes that RNA into DNA can amplify and detect it directly and sensitively.

So the correct answer is Reverse transcriptase-PCR.