When should I retest for HIV after a routine asymptomatic screening performed 2 days ago?

When to Retest HIV After Routine Asymptomatic Screening

For asymptomatic individuals with a negative routine HIV screening performed 2 days ago, retesting should be determined by ongoing HIV risk factors rather than a fixed time interval from the initial screen. 1

Immediate Retesting Not Indicated

• A routine asymptomatic screening performed 2 days ago does not require immediate retesting unless there was a specific high-risk exposure within the window period before that test. 1
• If the sexual encounter 2 days ago represents a new potential exposure (i.e., it occurred around the same time as or after the screening test), the initial screening would not capture infection from that exposure due to the window period. 2, 3

Understanding the Window Period

• Fourth-generation antigen/antibody tests (the current standard) can detect HIV approximately 18-24 days after exposure, while diagnostic nucleic acid testing (NAT) can detect infection at 10-14 days post-exposure. 2, 3
• The median window period for fourth-generation tests is 18 days (range 16-24 days), meaning most infections will be detected by 3-4 weeks after exposure. 3
• At 42 days post-exposure, the probability of a false-negative result with fourth-generation testing is only 0.01 (1%). 3

Risk-Based Retesting Recommendations

For individuals at very high risk (injection drug users, men who have sex with men with multiple partners, sex workers, sexual partners of HIV-positive persons):

• Retest at least annually. 1
• If the sexual encounter 2 days ago represents ongoing high-risk behavior, schedule retesting at 4-6 weeks after that exposure to capture the window period. 2

For individuals at increased but not very high risk (heterosexual persons with multiple partners, those in high-prevalence settings):

• Retest every 3-5 years. 1
• If the recent sexual encounter was an isolated higher-risk event, consider one-time retesting at 6-12 weeks post-exposure. 1, 2

For individuals at low ongoing risk (monogamous relationships with known HIV-negative partners):

• Routine repeated screening is not necessary. 1
• One-time screening is sufficient unless risk factors change. 1

Specific Timing If Recent Exposure Warrants Testing

If the sexual encounter 2 days ago involved high-risk circumstances (e.g., partner of unknown status, known HIV-positive partner, condomless sex with high-risk partner):

• Baseline testing now (if not already done within 72 hours of exposure) using fourth-generation antigen/antibody test, ideally with HIV RNA (NAT) if available. 1, 2
• Follow-up at 4-6 weeks post-exposure with laboratory-based fourth-generation test plus NAT. 2
• Final testing at 12 weeks (3 months) post-exposure with fourth-generation test, which is considered definitive to rule out infection. 4, 2

Critical Caveats

• If acute HIV symptoms develop (fever, rash, pharyngitis, lymphadenopathy), test immediately regardless of timeline, and include HIV RNA testing as antibody/antigen tests may still be negative during acute infection. 2
• Fourth-generation tests are preferred over rapid oral fluid tests, which are less sensitive for detecting recent infection. 2, 5
• The 12-week timepoint is considered definitive, as at least 95% of infected individuals will have detectable antibodies by 6 months, with most seroconverting much earlier. 5

Post-Exposure Prophylaxis Consideration

• If the exposure 2 days ago was high-risk (e.g., known HIV-positive partner), post-exposure prophylaxis (PEP) should be initiated within 72 hours of exposure and is most effective when started within 24 hours. 2
• If PEP is indicated but the 72-hour window has passed, it is too late to initiate. 2