HIV Pre-exposure Prophylaxis (PrEP) Testing

PrEP is a protocol that decreases the risk of acquiring HIV infection in people who do not have HIV but are at high risk of becoming infected. The PrEP protocol includes the use of antiretroviral medication. The CDC has developed guidelines that describe the rationale of PrEP, the patient populations for whom PrEP should be considered, and the management of patients who are prescribed PrEP therapy.

Patient management for PrEP includes laboratory testing before and during the PrEP protocol. The CDC guidelines indicate that persons who are under consideration for PrEP, and who are interested in taking PrEP voluntarily, should undergo laboratory testing to identify those for whom this intervention would be harmful or for whom it would present specific health risks that would require close monitoring.^1-4 In addition, as part of routine follow-up every 3 months, patients should be tested to confirm HIV-negative test status and assess for adverse effects.

Updated guidelines for laboratory testing and managing patients on PrEP were released in 2021 and contained significant changes for determining HIV status for patients who have not used PrEP versus patients who have used oral PrEP in the past 3 months or received a cabotegravir injection in the past 12 months. Please refer to the updated guidelines to choose the appropriate assays for the specific clinical scenario (see Figures 4a and 4b of the updated guidelines).

The current CDC guidelines are found at https://www.cdc.gov/hiv/pdf/risk/prep/cdc-hiv-prep-guidelines-2021.pdf

Before beginning PrEP, patients should have a baseline laboratory evaluation that includes testing for HIV, HBV, HCV, and sexually transmitted infections (STIs).¹

A documented laboratory-confirmed HIV negative result using an HIV-1/2 antigen/antibody immunoassay should be performed within a week of initiating PrEP. Additionally, tests to screen for syphilis, chlamydia, and gonorrhea (CT/NG) are also recommended for individuals who are prescribed PrEP. Screening for CT/NG should be performed using a nucleic acid amplification test (NAAT) and should include appropriate specimen types (eg, urogenital, throat, or rectal) based on reported exposure.⁵ HBV triple screening (HBsAg, anti-HBc, anti-HBsAg) can also be considered before prescribing PrEP; however, it is not recommended to wait for HBV test results before initiating the medication. HCV testing can be performed for patients with the appropriate risk factors (ie, men who have sex with men [MSM], transgender women [TGW] who have sex with men, and persons who inject drugs [PWID]) or if they have not been previously tested for HCV.

Other recommended baseline testing includes creatinine for evaluating renal function in those prescribed tenofovir DF-emtricitabine or tenofovir alafenamide-emtricitabine. In addition, a lipid panel is recommended for those prescribed tenofovir alafenamide-emtricitabine.

The Centers for Disease Control and Prevention (CDC) recommend follow-up testing at clinically relevant intervals for patients who are prescribed either oral or injectable PrEP.¹ 

All patients taking oral PrEP medications should have repeat HIV testing 3 months after initiation. Testing for sexually transmitted infections (STIs) (eg, syphilis, CT/NG) is also recommended at 3 months for patients with signs or symptoms of infection and for asymptomatic MSM and TGW. At 6 months, all patients should be tested for STIs, and kidney function should be monitored for those ≥50 years of age or who had an estimated creatine clearance (eCrCl) <90 ml/min at PrEP initiation. At 12 months, tests for eCrCl and lipid levels should be done for all patients whereas HCV testing is recommended only for MSM, TGW, and PWID.

All patients receiving cabotegravir injections should have HIV-1 RNA testing performed to assess HIV status one month after the initial injection, then at each bimonthly visit (beginning with the third injection — month 3). At least every 4 months (Q4 months), HIV and STI screening should be performed only for MSM and TGW. At least every 6 months (Q6 months), HIV and STI testing should be performed only for heterosexually active adults. At least every 12 months (Q12 months), testing for HIV and STI testing is recommended for all patients receiving cabotegravir injections. Laboratory tests for renal function, HBV, lipids, and liver function are not recommended for monitoring patients during cabotegravir injection use.

For information on HIV testing:
HIV 1 2 Antigen and Antibodies Fourth Generation with Reflexes | Quest Diagnostics

For information on HCV testing:
Hepatitis C Antibody with Reflex to HCV RNA PCR with Reflex to Genotype | Quest Diagnostics

For information on CT/NG testing:
Chlamydia trachomatis Neisseria gonorrhoeae RNA TMA | Quest Diagnostics

For information on HBV testing:
HBV triple screen panel with reflexes | Quest Diagnostics