Initiating Descovy After a Negative HIV 4th Generation Test
Yes, a patient can initiate Descovy (emtricitabine and tenofovir alafenamide) as PrEP after testing negative on a 4th generation HIV test, provided the test was performed within 7 days before starting PrEP. 1
Requirements for Starting PrEP with Descovy
HIV Testing Requirements
- A negative 4th generation HIV antigen-antibody test within 7 days before initiating PrEP is required 1
- For high-risk individuals, consider adding an HIV RNA test to rule out acute infection 1
- If no recent test is available, conduct testing and only initiate PrEP once negative results are confirmed 1
Clinical Scenario Considerations
- For patients who have had a recent high-risk exposure (within 72 hours), a 3-drug PEP regimen should be initiated first rather than immediate PrEP 1
- For individuals completing a 28-day course of PEP who remain at ongoing risk, a seamless transition to PrEP is recommended after confirming a negative 4th generation HIV test 1
Monitoring After PrEP Initiation
Follow-up Testing Schedule
- First follow-up visit: 1 month after initiation to assess adherence, tolerability, and ensure absence of primary HIV infection 1
- Subsequent follow-up: Every 3 months for:
Important Safety Monitoring
- PrEP prescriptions should not exceed 90 days without interval HIV testing 1
- Monitor renal function, as TAF-based PrEP has improved renal safety profile compared to TDF-based options 2, 3
- Annual HCV serologic testing (more frequent for high-risk individuals) 1
Special Considerations and Pitfalls
Potential Challenges in HIV Diagnosis During PrEP
- PrEP can alter and delay antibody responses and decrease plasma HIV RNA levels, making diagnosis challenging 1
- Any positive HIV screening test while on PrEP should prompt immediate confirmatory testing with HIV RNA and genotype testing 1
- If HIV infection is suspected or screening results are equivocal:
- Stop PrEP immediately
- Use alternative prevention methods
- Perform confirmatory testing
- If confirmed, initiate full ART promptly 1
Medication Adherence
- Adherence is critical for PrEP effectiveness
- Unanticipated interruptions in PrEP delivery (insurance coverage lapse, relocation, etc.) have been associated with seroconversions and should be avoided 1
- Studies show that Descovy (TAF/FTC) is non-inferior to Truvada (TDF/FTC) for HIV prevention when taken as prescribed 2, 3
Advantages of Descovy (TAF/FTC) vs. Truvada (TDF/FTC)
- Both regimens demonstrate high efficacy for HIV prevention 2, 3
- Descovy shows improved bone mineral density and renal safety biomarkers compared to Truvada 2, 3
- Descovy may be preferred for patients with or at risk for bone or renal issues 3
- Note that weight gain has been observed with Descovy compared to Truvada (median 1.7kg vs 0.5kg at 96 weeks) 3
Remember that while PrEP is highly effective, it is not 100% protective, and seroconversion despite excellent adherence has been reported in rare cases of high inoculum or viral resistance 1. Condom use should still be encouraged for additional protection against HIV and other STIs.