HIV Testing Protocol After Exposure Without PEP
If you did not take PEP after HIV exposure, you must undergo HIV testing at 12 weeks post-exposure using both a laboratory-based fourth-generation antigen/antibody test AND nucleic acid testing (NAT) to definitively rule out infection. 1, 2
Immediate Testing (As Soon As Possible)
- Obtain baseline HIV testing now with a laboratory-based fourth-generation antigen/antibody (Ag/Ab) test to establish your current HIV status 1, 2
- If available, add HIV NAT to baseline testing, especially if the exposure occurred within the past 10-14 days, as NAT can detect infection earlier than antibody tests 1, 3
- Do not use oral fluid rapid tests, as they are significantly less sensitive for detecting acute or recent infection compared to blood tests 1, 2
Follow-Up Testing Schedule
At 4-6 Weeks Post-Exposure
- Perform both laboratory-based Ag/Ab test AND diagnostic HIV NAT 1, 2
- This intermediate testing can identify early infection, though a negative result at this timepoint does not definitively rule out HIV 1, 4
- This is also an appropriate time to discuss starting PrEP if you have ongoing HIV exposure risk 1, 2
At 12 Weeks Post-Exposure (Final/Conclusive)
- Perform both laboratory-based Ag/Ab combination immunoassay AND diagnostic HIV NAT - this is considered conclusive by the CDC 1, 2, 4
- This 12-week timepoint accounts for the window period of HIV tests and provides definitive results 1, 4
- A negative result at 12 weeks with both tests definitively rules out HIV infection from this exposure 1, 2
Critical Considerations
Why 12 weeks is necessary: Fourth-generation Ag/Ab tests typically detect HIV 18-45 days post-exposure, while NAT can detect infection 10-14 days post-exposure 4, 3. The 12-week timepoint ensures adequate time has passed for all testing modalities to detect infection if present 1, 4.
If NAT is unavailable: While the CDC strongly recommends both Ag/Ab and NAT testing, if NAT is not accessible, laboratory-based Ag/Ab testing alone at 12 weeks should detect the vast majority of infections 4. However, this creates a diagnostic gap where highly infectious individuals with acute infection may go undetected 4.
Seek immediate evaluation if: You develop any illness compatible with acute retroviral syndrome (fever, rash, lymphadenopathy, pharyngitis) during the follow-up period, regardless of the interval since exposure 1, 2
Additional Testing
- Test for other sexually transmitted infections at baseline, as co-infections are common with similar exposure routes 2
- If there was potential hepatitis exposure, test for HBsAg and anti-HCV at baseline 2
Prevention Going Forward
- Strongly consider starting PrEP if you have ongoing or anticipated repeat HIV exposures, as this provides continuous protection rather than reactive post-exposure management 1, 2
- PrEP can be initiated after your baseline HIV test is negative, even before the 12-week conclusive testing is complete 1, 2