What laboratory tests should be monitored in a patient with HIV and possibly hepatitis B coinfection on Truvada (Emtricitabine/Tenofovir Disoproxil Fumarate) treatment?

Laboratory Monitoring for Truvada Treatment

Baseline Testing Before Initiating Truvada

All patients starting Truvada must undergo comprehensive baseline testing for hepatitis B virus infection (HBsAg, anti-HBc, anti-HBs), renal function (serum creatinine, estimated creatinine clearance), urine glucose, urine protein, and in patients with chronic kidney disease, serum phosphorus. 1

• Test for HBsAg, anti-HBc, and anti-HBs to identify hepatitis B coinfection status before starting therapy 2
• Obtain baseline serum creatinine and calculate estimated creatinine clearance 1
• Perform urinalysis including urine glucose and urine protein 1
• In patients with pre-existing chronic kidney disease, measure serum phosphorus at baseline 1
• Obtain baseline hepatic function tests (ALT, AST, alkaline phosphatase, bilirubin) 2
• Test for HIV antibodies in all patients to confirm HIV status 2
• Screen for hepatitis C antibody in patients with risk factors (injection drug use, foreign birth in endemic areas) 2
• Obtain complete blood count with platelets 2

Ongoing Monitoring During Treatment

Patients on Truvada require renal function monitoring (serum creatinine) every 12 weeks, hepatic panel every 12 weeks, and HBV DNA levels every 12-24 weeks if hepatitis B coinfected. 2

Renal Function Monitoring

• Monitor serum creatinine every 12 weeks throughout treatment 2
• Assess estimated creatinine clearance at each monitoring interval on a clinically appropriate schedule 1
• Check urine glucose and urine protein regularly during treatment 1
• In patients with chronic kidney disease, monitor serum phosphorus every 12 weeks 1

Hepatic Function Monitoring

• Obtain liver panel (ALT, AST, bilirubin, alkaline phosphatase) every 12 weeks 2
• More frequent monitoring (every 4 weeks) may be warranted in patients with baseline hepatic abnormalities or risk factors for hepatotoxicity 2

Hepatitis B Monitoring (if HBsAg-positive)

• Measure HBV DNA levels every 12-24 weeks during treatment 2
• Test HBeAg/anti-HBe every 24 weeks in patients who are initially HBeAg-positive 2
• Monitor for HBsAg clearance every 6-12 months in HBeAg-negative patients with persistently undetectable HBV DNA by PCR 2

HIV Monitoring (if HIV-positive)

• The American Medical Association recommends checking HIV RNA viral load within 6 weeks of starting therapy, then every 3 months until suppressed for 1 year, followed by every 6 months 3
• Monitor CD4 counts every 6 months until >250 cells/μL for at least 1 year with viral suppression 3

Laboratory Abnormalities to Monitor

Grade 3-4 laboratory abnormalities occur in approximately 30% of patients on emtricitabine/tenofovir and include elevated creatine kinase (9-12%), elevated ALT (2-5%), elevated AST (3-6%), neutropenia (3-5%), and hypertriglyceridemia (4-10%). 4

• Creatine kinase elevation (>4.0 × ULN) occurs in 9-12% of patients 4
• ALT elevation (>5.0 × ULN) occurs in 2-5% of patients 4
• AST elevation (>5.0 × ULN) occurs in 3-6% of patients 4
• Neutropenia (<750/mm³) occurs in 3-5% of patients 4
• Elevated triglycerides (>750 mg/dL) occur in 4-10% of patients 4
• Elevated serum amylase (>2.0 × ULN) occurs in 2-8% of patients 4

Critical Safety Considerations

Never discontinue Truvada abruptly in patients with hepatitis B coinfection, as severe acute exacerbations of hepatitis can occur; both tenofovir and emtricitabine have anti-HBV activity, and withdrawal requires close monitoring for several months. 2, 3

• Hepatitis B reactivation can occur after stopping Truvada, with severe hepatic flares reported 5
• Monitor ALT, AST, and HBV DNA closely for at least 6 months after discontinuation in HBsAg-positive patients 2
• Tenofovir can rarely cause Fanconi syndrome and renal insufficiency, requiring vigilant renal monitoring 2
• Three patients in one study developed reversible acute renal failure on tenofovir/emtricitabine, with one case of possible drug-induced acute tubular necrosis on biopsy 6

Dosage Adjustment Based on Renal Function

Truvada is not recommended for patients with creatinine clearance <30 mL/min; for creatinine clearance 30-49 mL/min, extend dosing interval to every 48 hours and monitor renal function closely. 1

• No dosage adjustment needed for creatinine clearance ≥50 mL/min 1
• For creatinine clearance 30-49 mL/min, dose every 48 hours instead of every 24 hours 1
• Truvada is not recommended for creatinine clearance <30 mL/min including hemodialysis patients 1
• Clinical response and renal function require close monitoring when using adjusted dosing intervals 1