Q:

Dear Doctor,

Hope you are well. I just wonder if I may ask the following. (I am very grateful for Dr’s assistance in advance).

In around early July (5th to 6th), Had unprotected oral sex (for about 30 seconds) and protected intercourse with a ‘young model’ expensive type prostitute.

During the intercourse, the penis might get soft but it was pretty sure that the rubber (of the condom) still covered almost the whole part of the penis. So, the intercourse did not continue but handjob was done instead.

Last week, did blood tests (at about 11-week interval since the incident). It seems that the test here in Hong Kong is different. It’s called ‘‘fourth generation tests or DUO tests’’, or‘‘combined antigen/antibody tests.

The test results of both antigen / antibody are negative. My doctor said it should be very safe by now and there is no need for another test.

However, I also note that some websites suggest that there is limitation with the aforesaid test, i.e. ‘‘levels of p24 (i.e. antigen) start to drop approximately a month after infection, but antibody is usually detectable by this stage. However in some extremely rare cases, p24 (i.e. antigen) may become undetectable before antibodies are detectable, and a fourth-generation test could give a false negative result.

So, how reliable is this test? Should a traditional test be taken after the 12-week mark?

Again, grateful for Doctor’s precious time and effort. My apology if the question is too long.

 

A:

You had a low-risk exposure, and a negative DUO test (mainly, the antibody test) at 11 weeks means you’re extremely unlikely to be HIV-infected. Don’t be bothered by p24 test; it’s useless to you at the moment. The general recommendation is to get a negative result after 12 weeks. A negative result at 11 weeks is good enough for most people. If you want a “perfect” ending, get a test after 12 weeks; if not, stop here and get back to your normal life.