What lab work is required before initiating Truvada (Emtricitabine/Tenofovir Disoproxil Fumarate) in patients, particularly those with a history of kidney disease or at risk of co-infection with hepatitis B or C?

Laboratory Testing Before Initiating Truvada

Before starting Truvada (emtricitabine/tenofovir disoproxil fumarate), you must obtain baseline renal function tests (serum creatinine and calculated creatinine clearance), urinalysis with urine glucose and urine protein, hepatitis B and C testing, HIV testing (if for PrEP), and a complete blood count with differential. 1

Essential Baseline Laboratory Tests

Renal Function Assessment (Critical)

• Calculate creatinine clearance using the Cockcroft-Gault equation - this is the required method for medication dosing decisions, not MDRD 2, 3
• Obtain serum creatinine at baseline 1
• Perform urinalysis checking for proteinuria, glucosuria, and albuminuria 2, 1
• Do NOT initiate Truvada if creatinine clearance is <60 mL/min for PrEP or <30 mL/min for HIV treatment 1
• Patients with chronic kidney disease also require serum phosphorus testing 1

Hepatitis Screening (Mandatory)

• Test for hepatitis B surface antigen (HBsAg) before initiation - this is critical because stopping Truvada in HBV-positive patients can cause severe hepatitis flares 1
• Test for hepatitis C antibody at baseline 2
• If HBV-positive, monitor ALT and HBV DNA levels regularly during treatment 2

HIV Testing (For PrEP Candidates)

• Perform combined HIV antibody and antigen testing before starting PrEP 1
• If recent exposure (<1 month) or acute HIV symptoms present (fever, fatigue, myalgia, rash), use an FDA-approved test for acute/primary HIV-1 infection 1
• Repeat HIV testing at least every 3 months once on PrEP 2, 1

Complete Blood Count and Chemistry Panel

• Obtain CBC with differential to assess for anemia, leukopenia, and thrombocytopenia 2
• Obtain comprehensive metabolic panel to assess hepatic function and nutritional status 2
• Fasting lipid profile should be obtained at baseline 2

High-Risk Populations Requiring Enhanced Screening

Patients at Increased Nephropathy Risk

• Black HIV-infected patients and those with advanced disease require baseline urinalysis and creatinine clearance due to higher risk of HIV-associated nephropathy 2
• Patients with diabetes, hypertension, or hepatitis C coinfection need baseline proteinuria screening 4
• Those over age 50 or with baseline creatinine clearance <90 mL/min require more frequent monitoring 2

Patients on Nephrotoxic Medications

• Avoid concurrent use with NSAIDs or other nephrotoxic agents - if unavoidable, obtain baseline renal function and monitor closely 1
• Check for drug interactions with boosted protease inhibitors or cobicistat, which increase tenofovir exposure 4

Additional Testing for Specific Populations

For HIV Treatment Candidates

• CD4 cell count at baseline 2
• HIV RNA viral load at baseline 2
• Tuberculosis screening with TST or interferon-gamma release assay 2
• HLA-B*5701 testing if abacavir is being considered as part of the regimen 2

For PrEP Candidates

• STI screening at baseline: gonorrhea and chlamydia nucleic acid amplification testing (genital and non-genital sites), syphilis serology 2
• Pregnancy test in women of childbearing potential 1

Critical Contraindications Based on Lab Results

Do not initiate Truvada if:

• Creatinine clearance <60 mL/min (for PrEP) 1
• Creatinine clearance <30 mL/min (for HIV treatment) 1
• Patient requires hemodialysis 1
• HIV test is positive or indeterminate (for PrEP candidates) 1
• Evidence of acute HIV infection with recent exposure 1

Common Pitfall to Avoid

Do not confuse creatinine elevation from proximal tubular secretion inhibition (caused by cobicistat, dolutegravir, or trimethoprim) with actual renal dysfunction - these medications can increase serum creatinine by 0.1-0.4 mg/dL without affecting true glomerular filtration 3. However, tenofovir can cause genuine nephrotoxicity including Fanconi syndrome, so any creatinine increase requires careful evaluation 1, 5.