Yes it is possible that an Elisa HIV test could pick up antibodies by 4 weeks. Everyone is different in how much time it takes them to develop antibodies that a test could detect. With the HIV Elisa test we say it is 95% accurate after 6 weeks but can take up to 3 months for a final result.
We do not see HIV being passed when receiving oral sex, but it is possible for other STI to be passed.
Have a look at our “Know your chances” web page, it provides information on your chances of getting or passing an STI depending on how you are having sex.
Please leave a comment to let us know if this answers your question or if you need more information.
For other readers, please feel free to leave a comment, or let us know if this was helpful.