Because PEP slows HIV from making copies of itself and thereby also slows the immune systems response to HIV infection, making antibodies. It is recommended that testing for HIV, by NAT should only begin 2 weeks after completing the full course of PEP (28 days). Testing by anti-HIV should begin 2 weeks after completing the full course of PEP and followed-up by another at 3 months. Because only 3 days of PEP was taken it was still necessary for you to wait 2 weeks after stopping PEP to reduce any uncertainty about when to start testing again. The scheduling of follow-up “routine check” is in keeping with testing guidelines but the follow-up was scheduled at 2 months rather than 3 because only 3 days of PEP were taken and the total time from possible HIV exposure would be approximately three months.
What the staff member has told you about 4th generation testing is correct. And, since you were not contacted about your NAT test result, it is correct to assume that your result was negative. Because both your anti-HIV and NAT test results were negative and because you were at very low risk of HIV infection, it is unlikely that your test results will change. However, in keeping with testing guidelines, a follow-up/routine check is still recommended, before a final confirmed result can be provided.