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HIV antigen formation

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  • HIV antigen formation

    Dear Doctor,

    I forgot to ask you during consultation few weeks ago about something. If I had cold infection a few days after possible HIV exposure, will it delay p24 antigen detection by 4th gen testing? I did test after 3 weeks exposure and turn out non-reactive after 15 minutes.

    I also read an article where you say the test is almost 100% after 20 days. Is it because the test kit used here is better?

  • #2
    Hi kaithleenyu

    A common cold will not delay p24 antigen detection by 4th gen testing.

    4th generation testing will start to detect p24 antigens as early as 14 days post infection but still with possible false negatives. It is only deemed conclusive if negative at the 28th day post infection.

    You can read more about HIV testing and the window period at the link below.

    HIV Window Period: When it comes to HIV testing, two of the most common questions we have are β€œWhen Can I Test for HIV?” and β€œAre My Results Conclusive?”


    • #3
      Hi Doctor,

      thank you for your reply. Just one last question. Does volume of infected fluid affect the duration for p24 antigens to get detected by the test?

      Have you encounter any cases in DTAP where the combo test was negative at 3 weeks but test was positive at 28 days?


      • #4
        Hi kaithleenyu,

        The concentration of viral particles does affect the chances of transmission. This is why blood is considered a higher risk while saliva is almost negligible risk. However, it does not affect the duration for p24 antigens detection, which are produced by actively replicating viruses rather than acquired through infected fluid.

        In response to your 2nd question, personally no. But if you are concerned, you may wish to speak to your doctor again.