PrEP Workup
A comprehensive PrEP (pre-exposure prophylaxis for HIV) workup requires documented HIV-negative status, assessment of renal function, hepatitis B screening, and testing for other sexually transmitted infections before initiating antiretroviral therapy.
Essential Laboratory Testing
HIV Status Confirmation
- HIV antibody/antigen testing (4th generation) is mandatory to confirm HIV-negative status before PrEP initiation, as starting PrEP in someone with undiagnosed HIV infection can lead to resistance 1
- If acute HIV infection is suspected (recent high-risk exposure with flu-like symptoms), add HIV RNA testing to detect infection during the window period before antibodies develop 1
Renal Function Assessment
- Baseline serum creatinine and calculated creatinine clearance (CrCl) are required before starting tenofovir-based PrEP regimens, as tenofovir can cause renal toxicity 2
- PrEP should not be initiated if CrCl is <60 mL/min due to increased risk of renal complications 2
Hepatitis B Screening
- Hepatitis B surface antigen (HBsAg), surface antibody (anti-HBs), and core antibody (anti-HBc) testing is essential 2
- This is critical because tenofovir treats hepatitis B, and discontinuing PrEP in someone with chronic hepatitis B can cause severe hepatitis flares 2
- Patients with chronic hepatitis B require specialized monitoring and should not abruptly stop PrEP 2
Sexually Transmitted Infection Screening
- Test for gonorrhea and chlamydia at exposed anatomic sites (pharyngeal, rectal, urogenital) based on sexual practices 1
- Syphilis screening with RPR or VDRL is required at baseline 1
- Hepatitis C antibody testing should be performed, particularly in men who have sex with men and persons who inject drugs 2
Clinical History and Physical Examination
Targeted History Elements
- Document specific HIV risk behaviors: condomless anal or vaginal sex, sex with HIV-positive partners, injection drug use, sex work, or recent bacterial STI diagnosis 3, 4
- Assess medication adherence capacity and barriers to consistent PrEP use 5
- Review current medications for potential drug interactions, particularly with tenofovir 2
- Screen for symptoms of acute HIV infection: fever, rash, lymphadenopathy, pharyngitis occurring within 2-4 weeks of high-risk exposure 1
Physical Examination Focus
- General physical examination is less diagnostically useful than history and laboratory testing for PrEP candidacy 3, 4
- Examine for signs of acute HIV infection if suspected: generalized lymphadenopathy, oral ulcers, or maculopapular rash 1
- Assess for signs of sexually transmitted infections: genital ulcers, urethral discharge, or inguinal lymphadenopathy 2
Pregnancy and Fertility Considerations
- Pregnancy testing is required for all persons of childbearing potential before initiating PrEP 2
- Counsel on fertility preservation options if desired, as PrEP itself does not affect fertility but should be discussed in comprehensive care 2
Additional Testing for Specific Populations
Hepatitis A Vaccination Status
- Check hepatitis A antibody status and vaccinate if non-immune, particularly for men who have sex with men 2
Baseline Complete Blood Count
- CBC with differential may identify cytopenias that could be relevant for monitoring, though not universally required 2
Common Pitfalls to Avoid
- Do not skip hepatitis B testing - this is the most commonly omitted but critically important test, as abrupt PrEP discontinuation in chronic hepatitis B can cause life-threatening hepatitis flares 2
- Do not rely on patient-reported HIV status alone - always confirm with laboratory testing, as many people with HIV are unaware of their status 1
- Do not initiate PrEP during the acute HIV window period without RNA testing if recent high-risk exposure occurred, as antibody tests may be falsely negative 1
- Do not forget anatomic site-specific STI testing - pharyngeal and rectal infections are frequently asymptomatic but require testing based on sexual practices 1