Laboratory Testing for Restarting PrEP After a 2-Year Hiatus

Mandatory HIV Testing Before Restart

The International Antiviral Society-USA guidelines recommend that HIV screening should ideally include both an HIV RNA test and a laboratory-based antigen-antibody test before restarting PrEP after a hiatus exceeding 14 days for tenofovir-based oral PrEP 1, 2, 3.
An HIV RNA (viral load) test with a lower limit of quantification of 50 copies/mL or lower is the gold standard for detecting acute HIV infection that antibody/antigen tests might miss 1, 2.
A fourth- or fifth-generation laboratory-based antigen-antibody test must be performed concurrently 1, 2, 4.

Baseline renal function must be reassessed before restarting PrEP, including serum creatinine with calculated creatinine clearance (CrCl) 5, 4.
The Cockcroft-Gault formula should be used for calculation 5.

Hepatitis B surface antigen (HBsAg) testing is essential because stopping tenofovir-based PrEP in HBV-positive patients can cause severe hepatitis flares, liver decompensation, and liver failure 4.

Hepatitis C antibody testing should be performed if not previously positive or if status unknown 6, 4.
STI screening by nucleic acid amplification test (NAAT) for Neisseria gonorrhoeae and Chlamydia trachomatis from all exposure sites should be performed 5, 6, 4.
Syphilis serology should be performed 6, 4.
Pregnancy testing should be performed for individuals of childbearing potential 5, 6, 4.
Hepatitis A IgG antibody testing should be performed for men who have sex with men and people who inject drugs (if not known to be immune) 6, 4.

If HIV test results from within the past 7 days are negative, PrEP can be initiated while awaiting further diagnostics and safety assessments 7.

At 1 month, repeat HIV antigen-antibody test to catch any breakthrough infections early 2, 6, 4.
Every 3 months (quarterly), HIV antigen-antibody testing, STI screening (gonorrhea, chlamydia, syphilis), and pregnancy testing if applicable should be performed 6, 4.
Creatinine clearance should be checked at first quarterly visit, then annually (or every 3-6 months if patient has risk factors) 6, 4.

Do not skip HIV RNA testing if available, as the 2-year gap represents substantial time for potential HIV exposure, and acute infection must be ruled out definitively 1, 2.
Do not restart PrEP with only a rapid antibody test, as this misses acute HIV infection and risks creating drug resistance 1, 4.
Do not forget hepatitis B testing, as abrupt discontinuation of tenofovir in HBV-positive patients can be life-threatening 4.
Do not assume prior renal function is still normal, as 2 years is sufficient time for renal status to change 4.