Before entering the subject, clarify that, the window period is the minimum and necessary time to do not only an HIV test, but any STD after a possible risk contact, therefore the window period for HIV would be such that:

  • Test at 10 days if we look for the virus RNA (by PCR)
  • 3 weeks test if we look for the p24 Antigen
  • 3-month test if we only look for Antibodies


As we can see in the graph, after a contact and possible contagion with someone with HIV, the first thing to seem logically is the virus itself, with which the techniques that should be used are those called PCR or Viral Load, which are precisely those techniques that directly look for viral RNA. But, why do it at 10 days and not at 7 days? The main reason is that, like any existing technique in the markup, they have a limit of detection, or in other words, they detect a certain amount of virus, which means that it is risky to make such an early test. that our organism is infected, these techniques could not reach the minimum detectable limits of viral RNA. For this reason you should always leave a margin of at least 3 more days, to ensure that there is enough genetic material to be detected.

Next, after the contact of our blood with the Virus HIV, there is a test called 4th Generation, which is looking for, simultaneously, Antibodies and p24 Antigen, but what is the p24 Antigen? It is a component that is found in the viral capsid of HIV and can be detected at 3 weeks after the possible infection.

And finally, we find the conventional tests, that like any other virus, after an initial exposure, our body will start to fight the virus with Antibodies, the problem of these tests, is that, until after 3 months, the levels of Antibodies They are not high enough in our body to be detected.

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