No Further Testing Required After 91 Days
You do not need to retest for HIV after receiving non-reactive results from the HIV Ag/Ab Combo ECLIA at both 63 and 91 days post-exposure, as this definitively rules out HIV infection. 1
Why 91 Days Is Conclusive
The CDC explicitly states that fourth-generation HIV Ag/Ab tests are considered conclusive after 12 weeks (84 days) of potential exposure. 1 Your testing at 91 days exceeds this threshold and provides definitive results.
Key timing considerations:
- Fourth-generation Ag/Ab combination tests detect HIV approximately 18-45 days post-infection 1
- The 12-week (84-day) window accounts for antiretroviral medication washout periods and the maximum window period of these tests 2
- Your 91-day test result is 7 days beyond the recommended definitive testing timepoint 1
Understanding Your Test Results
The ECLIA method you received is a fourth-generation laboratory-based Ag/Ab test, which is the recommended standard for HIV screening. 2 These tests detect both:
- HIV p24 antigen (appears earlier in infection)
- HIV antibodies (IgM and IgG) 2
Performance characteristics:
- Fourth-generation tests detect approximately 82% of acute infections that RNA testing would identify 3
- In high-prevalence populations, these tests have 99.9% specificity 3
- Two negative tests at 63 and 91 days provide extremely high confidence in excluding HIV infection 1
Important Caveats
The only scenario requiring additional testing would be if you:
- Took post-exposure prophylaxis (PEP) or pre-exposure prophylaxis (PrEP) medications, as antiretrovirals can suppress viral load and delay seroconversion 2, 4
- Had a new HIV exposure after your 91-day test
- Received a cabotegravir injection within the past year 2
If you took PEP, the CDC recommends both laboratory Ag/Ab testing AND nucleic acid testing (NAT) at 12 weeks post-PEP initiation (not post-exposure) because antiretrovirals can mask infection. 2 However, if you had no PEP and no new exposures, your 91-day result is definitive.
Clinical Bottom Line
Your two non-reactive fourth-generation Ag/Ab tests at 63 and 91 days conclusively exclude HIV infection from any exposure that occurred more than 91 days ago. 1 No further testing is medically indicated unless you have ongoing risk behaviors or new exposures. 2