What laboratory tests should a patient with HIV on Biktarvy (bictegravir/emtricitabine/tenofovir alafenamide) undergo for monitoring?

Laboratory Monitoring for Patients on Biktarvy

Patients on Biktarvy require HIV RNA viral load monitoring within 6 weeks of starting therapy, then every 3 months until suppressed for 1 year, followed by every 6 months; CD4 counts every 6 months until >250 cells/μL for 1 year with viral suppression; and baseline plus ongoing safety monitoring including hepatic transaminases, bilirubin, alkaline phosphatase, serum creatinine, and screening for sexually transmitted infections and hepatitis coinfection. 1, 2

Viral Load Monitoring Schedule

• Check HIV RNA at 2-4 weeks (preferably) or within 6 weeks after starting Biktarvy to assess initial virologic response 1, 2, 3
• Monitor every 3 months until HIV RNA <50 copies/mL for at least 1 year, then reduce frequency to every 6 months if adherence is excellent and viral suppression is maintained 1, 2
• If viral load rises above 50 copies/mL, repeat measurement within 4 weeks and reassess adherence 2, 4
• Virologic failure is defined as HIV RNA >200 copies/mL on at least 2 consecutive measurements 4

CD4 Count Monitoring Schedule

• Monitor CD4 counts every 6 months until >250 cells/μL for at least 1 year with concomitant viral suppression 1, 2
• Once this threshold is consistently maintained with sustained viral suppression, CD4 measurements can be discontinued unless antiretroviral therapy fails or immunosuppressive conditions develop 1, 2
• At virologic failure, repeat CD4 count 1

Baseline Safety Testing (Before or At Initiation)

Essential baseline laboratories include: 1, 3

• Hepatic function: AST, ALT, bilirubin, alkaline phosphatase 5
• Renal function: Serum creatinine and estimated creatinine clearance 5
• Complete blood count with platelet count 5
• Hepatitis B surface antigen, hepatitis B core antibody, and hepatitis B surface antibody to identify coinfection (critical since Biktarvy contains tenofovir alafenamide and emtricitabine, both active against HBV) 3, 6
• Hepatitis C antibody in patients with risk factors 5
• Fasting lipid panel (total cholesterol, LDL, HDL, triglycerides) 7

Ongoing Safety Monitoring

• Repeat hepatic and renal function tests at each visit (typically every 3-6 months aligned with viral load monitoring) 1
• Monthly clinical evaluations are recommended to identify adverse effects and assess adherence 5
• Screen for sexually transmitted infections at baseline and during ongoing care 1
• Lipid monitoring should continue periodically, as grade 3/4 LDL elevation occurred in 2.7% of patients on Biktarvy 7

Special Monitoring Considerations

Renal Function

• Bictegravir causes a small, non-progressive increase in serum creatinine (mean 0.1 mg/dL) due to inhibition of tubular secretion, not actual kidney damage 8
• Biktarvy can be used in patients with creatinine clearance ≥30 mL/min without dose adjustment 8, 6
• In patients with end-stage renal disease on hemodialysis, Biktarvy has been used successfully, though bictegravir levels are lower than in patients with normal renal function 8, 9

Hepatic Function

• Routine hepatic monitoring is not required unless baseline abnormalities exist or patients have risk factors for hepatotoxicity (hepatitis B/C coinfection, alcohol abuse) 5
• No dose adjustment is needed for mild-to-moderate hepatic impairment 8

Resistance Testing

• HIV genotype for reverse transcriptase and protease resistance should be obtained at baseline before starting therapy 1, 3
• Integrase genotype at baseline is not routinely recommended unless exposure to a partner with integrase inhibitor resistance is suspected 1
• If virologic failure occurs (HIV RNA >200 copies/mL on 2 consecutive tests), obtain resistance testing including integrase genotype while the patient remains on the failing regimen 1, 4

Common Pitfalls to Avoid

• Do not delay treatment initiation waiting for baseline laboratory results (except HIV RNA confirmation to rule out false positive) 3
• Do not switch therapy for single detectable viral loads between 50-200 copies/mL ("blips"); confirm with repeat testing first 4
• Do not discontinue Biktarvy abruptly in patients with hepatitis B coinfection, as this can cause severe hepatitis flares; both tenofovir alafenamide and emtricitabine treat HBV 1, 3, 6
• Do not perform HLA-B*5701 testing before Biktarvy initiation, as this is only required for abacavir-containing regimens 1