What laboratory tests are recommended for a patient taking Truvada (emtricitabine and tenofovir disoproxil fumarate) for HIV treatment or PrEP?

Truvada Monitoring Labs

For patients on Truvada (emtricitabine/tenofovir disoproxil fumarate), perform HIV testing every 3 months using combined antigen-antibody assays, renal function monitoring every 6-12 months (or more frequently if risk factors present), and quarterly STI screening at all exposure sites. 1, 2, 3

Pre-Initiation Laboratory Testing

Before starting Truvada, the following baseline tests are mandatory:

• HIV testing: Combined HIV antibody and antigen assay (laboratory-based) 1, 2

  • Add HIV RNA testing if acute HIV infection is suspected or if the patient has recently taken antiretrovirals or received cabotegravir injection within the past year 1, 3
  • Testing must be completed within 7 days before initiation 1

• Renal function: Serum creatinine and estimated creatinine clearance using Cockcroft-Gault formula 1, 2, 3

  • Do not initiate Truvada if creatinine clearance is <60 mL/min 1, 2, 3

• Hepatitis B surface antigen (HBsAg) 1, 2, 4

• Hepatitis C antibody (IgG) 1, 4

• STI screening: Nucleic acid amplification testing (NAAT) for gonorrhea and chlamydia at all potential exposure sites (urogenital, rectal, pharyngeal) 1, 3, 4

• Syphilis testing 1

• Pregnancy testing for individuals of childbearing potential 2, 4

Ongoing Monitoring Schedule

Every 3 Months (Quarterly):

• HIV testing: Combined antigen-antibody assay (laboratory-based) 1, 2, 3

  • This is the most critical monitoring parameter—PrEP prescriptions should not exceed 90 days without interval HIV testing 1, 2

• STI screening: Three-site NAAT testing for gonorrhea and chlamydia (rectal, pharyngeal, urogenital) 1, 3

• Syphilis testing 1, 2

• Pregnancy testing for individuals of childbearing potential 2, 4

• Clinical assessment: Adherence evaluation, risk behavior assessment, side effects review, and willingness to continue PrEP 1

Every 6-12 Months:

• Renal function monitoring: Serum creatinine and estimated glomerular filtration rate (eGFR) 1, 2, 3

More Frequent Renal Monitoring (Every 3-6 Months) Required For:

• Patients >50 years of age 2, 3
• Patients taking medications for hypertension or diabetes 2, 3
• Patients with baseline eGFR <90 mL/min 2, 3
• Patients with pre-existing renal dysfunction 1

At Least Annually:

• Hepatitis C serologic testing, with more frequent testing for high-risk individuals (e.g., people who inject drugs) or those with elevated transaminase levels 1

First Follow-Up Visit

The CDC Taiwan guidelines recommend the first clinical follow-up within 30 days of PrEP initiation to assess adherence, tolerability, and ensure absence of primary HIV infection 1. The IAS-USA panel also recommends a 1-month follow-up visit for these purposes 1.

Critical Safety Considerations

Renal toxicity monitoring is essential because glomerular dysfunction may occur with Truvada therapy, particularly in individuals older than 50 years, though it is usually reversible 1. The most common adverse reactions (≥10%) include diarrhea, nausea, fatigue, headache, dizziness, depression, insomnia, abnormal dreams, and rash 5.

For patients with chronic hepatitis B: Use extreme caution when discontinuing Truvada, as there is risk of acute hepatitis flares or hepatic decompensation, particularly in those with cirrhosis 3.

Special Testing Considerations

If HIV infection is suspected during PrEP use, testing becomes more complex because antiretrovirals can suppress HIV viral load, delay seroconversion, and decrease the ability to detect HIV infection 1. In this scenario, both a laboratory-based antigen-antibody test and diagnostic HIV RNA (NAT) are recommended 1.

For patients who seroconvert while taking PrEP, HIV genotypic resistance testing should be performed 1.