How do I order a hepatitis B (HBV) viral load test?

How to Order a Hepatitis B Viral Load Test

Order the test as "HBV DNA quantitative PCR" or "Hepatitis B viral load" using a real-time PCR assay with a lower limit of detection ≤30 IU/mL, and ensure the result is reported in International Units per milliliter (IU/mL). 1

Test Ordering Specifications

Proper Test Name and Method

• Request the test as "HBV DNA quantitative" or "Hepatitis B viral load by PCR" 1, 2
• Specify that results must be reported in International Units per milliliter (IU/mL) using the WHO standard 97/746, not copies/mL 2
• The assay must use real-time PCR technology with a lower limit of detection of ≤30 IU/mL to avoid missing 40-60% of HBeAg-negative patients with active disease 1, 2

Sample Type

• Order on serum or EDTA plasma (both are acceptable) 1, 3
• No difference in performance has been observed between plasma and serum samples 3

Essential Context Required Before Ordering

You must know the patient's HBsAg and anti-HBc status before ordering HBV DNA. 1

Initial Screening Algorithm

• First, test for HBsAg and anti-HBc (at minimum) in all patients 1
• Only order HBV DNA if HBsAg and/or anti-HBc is positive 1
• For patients at risk of HBV reactivation (receiving immunosuppression or chemotherapy), also test for anti-HBs 1

Additional Required Information for Interpretation

• HBeAg status is essential for interpreting viral load thresholds 1, 2
• ALT levels must be obtained concurrently to guide treatment decisions 1, 2
• Prior treatment history, especially lamivudine exposure, affects resistance patterns 2

Clinical Scenarios Requiring HBV DNA Testing

Diagnosis and Risk Stratification

• Chronic HBV infection confirmation: HBV DNA is one of the criteria for diagnosing chronic hepatitis B 1
• Occult HBV detection: Test in HBsAg-negative patients with anti-HBc positivity who have cryptogenic liver disease, are undergoing immunosuppression, or are solid organ donors 1
• HBeAg-negative chronic hepatitis B: HBV DNA is the only marker of viral replication that can be monitored in these patients 1, 2

Monitoring During Immunosuppression

• Before starting immunosuppressive therapy: Establish baseline viral load in all HBsAg-positive or anti-HBc-positive patients 1
• During monitoring strategy (for moderate or low-risk HBV reactivation): Check HBV DNA at 1- to 3-month intervals 1
• Monthly monitoring through treatment and every 3 months thereafter for patients receiving anti-CD20 therapy 1

Treatment Decisions and Monitoring

• Pre-treatment baseline: Measure HBV DNA within 24 hours before starting antiviral therapy 2
• Treatment response assessment: A ≥1 log₁₀ IU/mL reduction within 3 months indicates antiviral effect 2
• Distinguishing inactive carriers from active disease: Serial HBV DNA testing is mandatory in HBeAg-negative patients with low viral loads and normal ALT 1, 2

Critical Viral Load Thresholds for Clinical Decision-Making

HBeAg-Positive Patients

• ≥20,000 IU/mL defines active viral replication and is the threshold for considering treatment when combined with elevated ALT or moderate-to-severe histologic disease 1, 2
• This threshold corresponds to the limit of detection of older hybridization-based assays and optimally identifies 90% of patients with active disease 1

HBeAg-Negative Patients

• ≥2,000 IU/mL is the optimal cutoff to differentiate chronic hepatitis B from inactive carrier state, particularly with normal ALT 1, 2
• Using the higher 20,000 IU/mL threshold in HBeAg-negative patients misses 30% of patients with active disease even after multiple sequential tests 1

Healthcare Workers and High-Risk Procedures

• <1,000 IU/mL (approximately <200 IU/mL) is the threshold below which HBeAg-negative healthcare workers may perform exposure-prone procedures 1
• Viral loads must be measured using assays capable of detecting levels well below 200 IU/mL (real-time PCR with detection limit of 10-30 IU/mL) 1

Common Pitfalls to Avoid

Assay Selection Errors

• Do not use hybridization-based assays with detection limits of 200 IU/mL or higher, as they miss 40-60% of HBeAg-negative patients with active disease 1, 2
• Do not accept results in copies/mL without conversion; insist on IU/mL reporting (1 IU ≈ 5.4 copies/mL, though this varies by assay) 2

Interpretation Errors

• Do not rely on a single HBV DNA measurement in HBeAg-negative patients with low viral loads and normal ALT; serial testing over 3-6 months is mandatory to distinguish inactive carriers from active disease 1, 2
• Do not assume low viral load means no disease: Cirrhosis can develop with viral loads <2,000 IU/mL 1, 2
• Do not use HBeAg alone to assess infectivity; HBeAg-negative patients can have viral loads ≥100,000 IU/mL due to pre-core mutants 1

Monitoring Errors

• Do not order HBV DNA without concurrent ALT testing; both are required for monitoring patients at risk of reactivation 1
• Do not forget that IVIG can cause false-positive anti-HBc; test for HBV markers before IVIG administration when possible 1
• Do not stop monitoring too early: Continue HBV DNA monitoring for at least 6 months after discontinuation of immunosuppressive therapy (12 months for B-cell depleting agents) 1

1, 2, 3