What explains a positive RT-PCR for HIV-1 followed by a negative Western blot?

A positive RT-PCR result for HIV-1 followed by a negative Western blot can indeed be explained by the higher sensitivity of RT-PCR, particularly in the early stages of HIV infection. RT-PCR detects viral RNA and can identify the presence of HIV before antibodies have developed, which is why it may yield a positive result early on.

In the initial phases of infection, the body may not have produced sufficient antibodies for detection using the Western blot, which relies on the presence of these antibodies to confirm an HIV diagnosis. Therefore, even if the virus is present and replicating, the Western blot might come back negative due to the lack of an immune response that would yield detectable antibodies. This scenario illustrates the significance of using a combination of diagnostic tests to determine HIV infection, particularly in the early stages.