What lab monitoring is required for patients taking Truvada (Emtricitabine/Tenofovir Disoproxil Fumarate) for HIV-1 infection or Pre-Exposure Prophylaxis (PrEP)?

Laboratory Monitoring for Truvada (Emtricitabine/Tenofovir Disoproxil Fumarate)

All patients taking Truvada require HIV testing every 3 months without exception, with renal function monitoring at baseline and every 6 months (or every 3 months if risk factors present), plus hepatitis B testing before initiation and STI screening every 3 months. 1, 2, 3

Pre-Initiation Testing (Required Before First Dose)

Mandatory Tests Before Starting Truvada

• HIV testing with 4th generation combined antibody/antigen assay is absolutely required and must be negative before initiating Truvada for either treatment or PrEP 1, 2, 3
• Add HIV RNA testing if any clinical suspicion of acute HIV infection exists (fever, rash, lymphadenopathy, pharyngitis, recent high-risk exposure within past month) - withhold Truvada until RNA results return negative 1, 2, 3
• Serum creatinine with calculated creatinine clearance using Cockcroft-Gault formula is required; Truvada is contraindicated if CrCl <60 mL/min for PrEP or <30 mL/min for HIV treatment 1, 2, 3
• Hepatitis B surface antigen (HBsAg) testing is essential because stopping Truvada in HBV-positive patients can cause severe hepatitis flares or hepatic decompensation 1, 2, 3
• Hepatitis C antibody testing should be performed at baseline 1, 2
• STI screening with nucleic acid amplification testing (NAAT) for gonorrhea and chlamydia from all exposure sites (pharyngeal, rectal, urogenital) plus syphilis serology 1, 2
• Pregnancy testing for individuals of childbearing potential 1, 2
• Urine glucose and urine protein should be assessed at baseline 3
• Serum phosphorus if chronic kidney disease is present 3

Critical Pitfall to Avoid at Initiation

Starting Truvada during undiagnosed acute HIV infection leads to drug resistance, particularly M184V/I mutations, which permanently compromises future treatment options 2. If the patient reports flu-like symptoms or had high-risk exposure within the past month, you must add HIV RNA testing before prescribing Truvada 1, 2, 3.

Ongoing Monitoring Schedule

First Month Follow-Up (30 Days After Initiation)

• HIV antibody/antigen testing at 1 month to catch any breakthrough infections early 1, 2
• Assessment of adverse effects, adherence, and willingness to continue 4, 1
• Do not prescribe more than 30 days of Truvada at the first visit 4

Every 3 Months (Quarterly Monitoring - Non-Negotiable)

• HIV antibody/antigen testing every 3 months is mandatory - never prescribe more than 90 days of Truvada without interval HIV testing 1, 5, 2, 3
• STI screening every 3 months: NAAT for gonorrhea and chlamydia from all exposed anatomic sites, plus syphilis serology 1, 2
• Pregnancy testing at each visit for individuals of childbearing potential 1, 2
• Adherence assessment and counseling at every visit 4, 1, 2
• Risk behavior assessment and provision of condoms 1

Every 6 Months (Renal Function Monitoring)

• Serum creatinine and estimated creatinine clearance every 6 months for standard-risk patients 1, 2
• Increase renal monitoring to every 3 months if any of these risk factors are present: age >50 years, baseline CrCl <90 mL/min, diabetes, hypertension, or chronic kidney disease 1, 2

Annual Monitoring

• Hepatitis C antibody testing at least annually, but increase to every 6 months for high-risk individuals (people who inject drugs, MSM who use recreational drugs during sex) 1, 2

Special Monitoring Situations

If Creatinine Elevation Occurs

• Do not discontinue Truvada based solely on mild creatinine elevation if CrCl remains >60 mL/min - this represents expected pharmacologic effects 2
• Check for proteinuria and recheck kidney function in 1-3 months 2
• Increase monitoring frequency to every 3 months for patients with any creatinine elevation 2
• Discontinue Truvada only if CrCl falls below 60 mL/min for PrEP or below 30 mL/min for HIV treatment 3

If HIV Infection Occurs During PrEP

• Immediately add a boosted protease inhibitor and/or dolutegravir to the TDF/FTC while awaiting HIV RNA and resistance testing results 1, 2
• Order HIV genotypic resistance testing and establish linkage to HIV care 1, 2
• Switch to a recommended initial antiretroviral treatment regimen once HIV is confirmed 1

If Stopping Truvada in Hepatitis B Positive Patients

• Monitor liver function closely after discontinuation due to risk of acute hepatitis flares or hepatic decompensation 1, 3
• Consider continuing Truvada or switching to alternative HBV therapy rather than stopping abruptly 3

Key Monitoring Principles

The Non-Negotiable Rule

Never prescribe more than 90 days of Truvada without documented negative HIV testing - this is the single most important monitoring requirement to prevent drug resistance if undiagnosed HIV infection occurs 1, 5, 2.

Renal Monitoring Nuances

The FDA label states to assess renal function "on a clinically appropriate schedule," but guidelines clarify this means every 6 months for standard-risk patients and every 3 months for high-risk patients 1, 2, 3. Mild creatinine elevations are common and expected with tenofovir, so avoid overreacting by stopping Truvada unless CrCl drops below the threshold of 60 mL/min for PrEP 2, 3.

STI Screening Rationale

STIs increase HIV acquisition risk, so quarterly screening serves dual purposes: detecting infections that need treatment and identifying patients at ongoing high risk who benefit most from continued PrEP 1, 2.