Question

HIV RNA detection by PCR (viral load assay) can reliably detect as low as how many copies of viral RNA per millilitre of blood?

• A. 30 copies viral RNA/ml of blood
• B. 40 copies viral RNA/ml of blood
• C. 50 copies of viral RNA/ml of blood
• D. 60 copies of viral RNA/ml of blood

Hint:

Routine clinical viral load assays bottom out at this two-digit copy number.

Answer 1

The Correct Option is B

Step 1: The HIV viral load assay uses RT-PCR to quantify HIV RNA, reporting the result as the number of copies of HIV RNA per millilitre of serum or plasma. It is used to monitor disease progression and the response to antiretroviral therapy.

Step 2: Standard commercial viral load assays can reliably detect as few as 40 copies of HIV RNA per millilitre of plasma. Hence the correct answer is option b (40 copies/ml).

Step 3: The other figures (30, 50, 60 copies) are not the validated lower limit of standard assays. Note that specialised research based assays can push detection down to a single copy per millilitre, but that is not the routine clinical cut-off being asked here.