57.3 Viral Hepatitis B & C: Long-Term Monitoring & DAA Therapy

Chronic Hepatitis B Virus (HBV): Serologic Profiling, Natural History Phases & Treatment Indications

Hepatitis B virus (HBV) is a partially double-stranded DNA virus of the Hepadnaviridae family. Globally, more than 250 million individuals live with chronic HBV infection. In primary care, correctly interpreting serologic markers, identifying disease phases, and recognizing indications for antiviral therapy are vital to preventing cirrhosis, end-stage liver disease, and hepatocellular carcinoma (HCC).

Comprehensive Serologic Interpretation Panel

                    HEPATITIS B SEROLOGIC PROFILES & INTERPRETATION

   Clinical Scenario       HBsAg    Anti-HBs   Anti-HBc Total   Anti-HBc IgM   HBeAg    HBV DNA
   ═══════════════════════════════════════════════════════════════════════════════════════════════
   Susceptible             Neg      Neg        Neg              Neg            Neg      Undetectable
   (Never exposed)

   Immunity via            Neg      POS        Neg              Neg            Neg      Undetectable
   Vaccination                      (>=10 mIU/mL)

   Immunity via Past       Neg      POS        POS (IgG)        Neg            Neg      Undetectable
   Natural Infection

   Acute Hepatitis B       POS      Neg        POS              POS            POS      Very High
   Infection

   Chronic Hepatitis B     POS      Neg        POS (IgG)        Neg            +/-      Variable
   (> 6 Months)

   Isolated Total          Neg      Neg        POS (IgG)        Neg            Neg      Undetectable
   Anti-HBc Positive*                                                                   or Low
   ═══════════════════════════════════════════════════════════════════════════════════════════════
   *Isolated Anti-HBc Differential: 1) Distant resolved infection with waning anti-HBs titers (most common);
   2) Occult HBV infection (detectable low-level HBV DNA in serum or liver); 3) False-positive test result;
   4) Window period of acute infection (HBsAg has cleared, anti-HBs not yet detectable; anti-HBc IgM is positive).

The Four Clinical Phases of Chronic Hepatitis B

Chronic HBV is a dynamic disease classified into four distinct phases based on HBeAg status, serum HBV DNA viral load, serum ALT, and the presence of ongoing necroinflammatory liver injury:

1. Phase 1: Immune Tolerant (HBeAg-Positive Chronic Infection):
   • Characteristics: HBeAg positive, extremely high serum HBV DNA levels (frequently >1,000,000 to >100,000,000 IU/mL), normal serum ALT, and minimal or no inflammation or fibrosis on histology.
   • Epidemiology: Classically seen in vertical (perinatal) transmission in endemic areas (e.g., East Asia). The immature immune system tolerates viral antigens without immune-mediated hepatocyte destruction.
   • Management: Antiviral treatment is NOT indicated. Antivirals show poor seroconversion rates in this phase. Monitor serum ALT and HBV DNA every 6 months to detect transition to the immune active phase.
2. Phase 2: Immune Active (HBeAg-Positive Chronic Hepatitis):
   • Characteristics: HBeAg positive, high HBV DNA levels (>20,000 IU/mL), elevated serum ALT (>2 times the upper limit of normal [ULN]), and active histologic necroinflammation and progressive fibrosis.
   • Pathophysiology: Host CD8+ T-lymphocytes recognize viral antigens on hepatocyte membranes, driving immune-mediated lysis of infected hepatocytes.
   • Management: Antiviral treatment is DEFINITIVELY indicated to suppress viral replication, halt fibrosis progression, and promote HBeAg seroconversion to anti-HBe.
3. Phase 3: Inactive Carrier (HBeAg-Negative Chronic Infection / Immune Control):
   • Characteristics: HBeAg negative, anti-HBe positive, low or undetectable serum HBV DNA (<2,000 IU/mL), consistently normal ALT, and inactive/stable liver histology.
   • Management: Antiviral treatment is not routinely indicated. Patients require lifelong surveillance with serum ALT and HBV DNA every 6 to 12 months, as reactivation can occur spontaneously or during immunosuppression.
4. Phase 4: HBeAg-Negative Immune Active (Immune Escape / Pre-Core Mutant):
   • Characteristics: HBeAg negative, anti-HBe positive, elevated ALT, and fluctuating elevated serum HBV DNA (>2,000 IU/mL).
   • Pathophysiology: Harbor viral variants containing mutations in the pre-core (G1896A stop codon) or basal core promoter (BCP) region that prevent synthesis of HBeAg while preserving robust viral replication. The immune system attacks the liver despite the absence of circulating HBeAg.
   • Management: Antiviral treatment is DEFINITIVELY indicated, as this phase is associated with rapid progression to cirrhosis, decompensation, and HCC.

AASLD Indications for Initiating Antiviral Therapy

Treatment is indicated in patients meeting the following clinical criteria:

• Elevated ALT (>2x ULN) AND Elevated HBV DNA: (>20,000 IU/mL if HBeAg-positive; >2,000 IU/mL if HBeAg-negative). Note: AASLD defines ULN for ALT as 35 U/L for men and 25 U/L for women.
• Any Patient with Cirrhosis (Compensated or Decompensated): Any cirrhotic patient with detectable serum HBV DNA, regardless of ALT level, requires immediate, indefinite antiviral therapy.
• Evidence of Advanced Fibrosis / Cirrhosis (>=F2) on elastography or liver biopsy with elevated HBV DNA (>2,000 IU/mL), regardless of ALT.
• Prevention of Perinatal Transmission: Pregnant women with high viral loads (HBV DNA >200,000 IU/mL or >5.3 log10 IU/mL) measured at 24 to 28 weeks gestation must receive tenofovir (TDF) starting at 28 to 32 weeks gestation through delivery to prevent mother-to-child transmission (given in addition to neonatal infant HBIG and HBV vaccination within 12 hours of birth).

Preferred First-Line Oral Antivirals, Long-Term Safety & Reactivation Prophylaxis

Historic therapies with low genetic barriers to resistance (e.g., lamivudine, adefovir) are obsolete due to five-year resistance rates exceeding 70%. Current AASLD guidelines recommend oral nucleos(t)ide analogues with a high genetic barrier to resistance as first-line monotherapy.

First-Line Oral Nucleos(t)ide Analogues

                 FIRST-LINE ORAL ANTIVIRAL AGENTS FOR CHRONIC HEPATITIS B

   Medication            Dosage                 Resistance Rate   Clinical Selection & Safety Nuances
   ═════════════════════════════════════════════════════════════════════════════════════════════════════
   Entecavir (ETV)       0.5 mg PO once daily   < 1.2% at 5 yrs   • Highly potent guanosine nucleoside analogue
                         (1.0 mg if lamivudine-                   • Dose-reduce for CrCl <50 mL/min
                         refractory / decomp)                     • Ineffective if prior lamivudine resistance
                                                                  • Must rule out HIV coinfection before use
                                                                    (selects for M184V mutation in HIV)

   Tenofovir Disoproxil  300 mg PO once daily   0% documented     • Highly potent nucleotide analogue
   Fumarate (TDF)                                                 • Preferred agent in pregnancy (Class B)
                                                                  • Active against lamivudine-resistant strains
                                                                  • Safety Concerns: Proximal renal tubular
                                                                    dysfunction (Fanconi syndrome) and loss of
                                                                    bone mineral density (osteopenia/osteoporosis)

   Tenofovir             25 mg PO once daily    0% documented     • Phosphonamidate prodrug of tenofovir
   Alafenamide (TAF)     with food                                • Enters hepatocytes efficiently, resulting in
                                                                    >90% lower circulating plasma tenofovir levels
                                                                    compared to TDF
                                                                  • Significantly superior renal and bone safety
                                                                  • PREFERRED over TDF in: Age >=60 years,
                                                                    osteopenia/osteoporosis, or CrCl 15-50 mL/min
   ═════════════════════════════════════════════════════════════════════════════════════════════════════

• Treatment Duration & Monitoring:
  • In the vast majority of patients (and all cirrhotic patients), oral antiviral therapy is lifelong, as covalently closed circular DNA (cccDNA) persists within hepatocyte nuclei despite suppressed serum DNA.
  • Monitor serum ALT and quantitative HBV DNA every 3 to 6 months until viral suppression is achieved, then every 6 months indefinitely.
  • Monitor renal function (serum creatinine, eGFR, urinalysis for proteinuria/glycosuria, and serum phosphorus) every 6 months in patients receiving TDF.

Prevention of Hepatitis B Reactivation During Immunosuppression

Hepatitis B reactivation during cancer chemotherapy or systemic immunosuppressive therapy can trigger fulminant hepatic failure and death. Reactivation occurs when immunosuppression allows exponential uninhibited viral replication, followed by immune reconstitution that catastrophically destroys infected hepatocytes:

• Mandatory Pre-Treatment Screening: All patients scheduled to receive cancer chemotherapy, systemic immunosuppressive biologics, or high-dose corticosteroids must undergo baseline screening with HBsAg AND Total Anti-HBc.
• High-Risk Regimens: Therapies that deplete B-cells (e.g., anti-CD20 monoclonal antibodies: rituximab, ofatumumab, obinutuzumab) carry a >10% to 20% risk of HBV reactivation, even in patients who are HBsAg-negative and only total anti-HBc positive (resolved natural infection). Other high-risk agents include anthracycline chemotherapy and high-dose prednisone (>=20 mg daily for >=4 weeks).
• Prophylactic Management:
  • Any HBsAg-Positive Patient: Mandatory initiation of prophylactic antiviral therapy (entecavir or tenofovir) prior to or concurrently with the start of immunosuppression, continuing for at least 12 to 24 months after the cessation of immunosuppressive therapy.
  • HBsAg-Negative / Total Anti-HBc Positive Patients: If receiving B-cell depleting therapy (rituximab), prophylactic antiviral therapy is mandated. For lower-risk immunosuppression, serial monitoring of ALT and HBV DNA every 1 to 3 months with prompt pre-emptive antiviral initiation upon detectable viral DNA is acceptable.

Chronic Hepatitis C Virus (HCV): Natural History, Direct-Acting Antivirals & Post-SVR Surveillance

Hepatitis C virus (HCV) is an enveloped, positive-sense, single-stranded RNA virus of the Flaviviridae family. Spontaneous viral clearance occurs in only 15% to 25% of acutely infected individuals; the remaining 75% to 85% develop chronic Hepatitis C infection. Over a 20- to 30-year duration, 20% to 30% of chronically infected individuals progress to cirrhosis, liver failure, and hepatocellular carcinoma.

Universal Screening & Diagnostic Algorithm

• Universal Screening Guidelines: The Centers for Disease Control and Prevention (CDC) and the U.S. Preventive Services Task Force (USPSTF) recommend universal one-time HCV screening for all adults aged 18 years and older, as well as screening during each pregnancy. Ongoing periodic screening is indicated for individuals with ongoing risk factors (e.g., injection drug use, hemodialysis).
• Two-Step Diagnostic Sequence:
  1. Step 1: Anti-HCV Antibody with Reflex Testing: Initial screening uses an enzyme immunoassay for anti-HCV antibodies.
  2. Step 2: Quantitative HCV RNA PCR: Reflexively performed on all antibody-positive specimens.
     • Anti-HCV Positive / HCV RNA Undetectable: Indicates resolved past infection (spontaneous clearance or prior successful treatment) or a biological false-positive. No treatment indicated.
     • Anti-HCV Positive / HCV RNA Detectable: Confirms active chronic HCV infection. Proceed to pre-treatment evaluation.

Pre-Treatment Evaluation Checklist

Before initiating direct-acting antiviral (DAA) therapy, clinicians must complete a standardized clinical safety assessment:

1. Screen for Hepatitis B Coinfection (Black Box Warning): DAAs rapidly eradicate HCV, removing the suppressive regulatory effect that HCV exerts on HBV replication. In coinfected patients, clearing HCV can trigger fatal acute Hepatitis B reactivation. Test every patient for HBsAg and Total Anti-HBc prior to initiating DAA therapy; if active HBV is detected, treat HBV concurrently.
2. Staging Liver Fibrosis & Cirrhosis: Calculate the FIB-4 index and/or perform transient elastography to differentiate non-cirrhotic patients (F0-F2) from those with advanced fibrosis (F3) or cirrhosis (F4). If cirrhosis is present, calculate the Child-Pugh score to distinguish compensated (Class A) from decompensated (Class B or C) disease.
3. Screen for Critical Drug-Drug Interactions (DDIs): Review all concomitant medications using the University of Liverpool Hepatitis Drug Interactions database.

Modern Pangenotypic Direct-Acting Antiviral (DAA) Regimens

DAAs directly target specific non-structural viral proteins essential for viral replication. Modern all-oral, pangenotypic regimens cure >95% to 98% of patients across all HCV genotypes (1 through 6) with an 8- to 12-week course:

                 PREFERRED FIRST-LINE PANGENOTYPIC DAA REGIMENS

   Regimen                 Components & Mechanism         Dosing & Duration    Clinical Pearls & Contraindications
   ═════════════════════════════════════════════════════════════════════════════════════════════════════════════
   Glecaprevir /           • Glecaprevir (100 mg):        3 tablets taken      • 8-Week duration in treatment-naive
   Pibrentasvir              NS3/4A Protease Inhibitor    TOGETHER once daily    patients (with or without Child-Pugh A)
   (Mavyret)               • Pibrentasvir (40 mg):        WITH FOOD for        • ABSOLUTELY CONTRAINDICATED in
                             NS5A Replication Complex     8 WEEKS                decompensated cirrhosis (Child-Pugh B or C)
                             Inhibitor                                           due to risk of fatal drug-induced
                                                                                 hepatic decompensation

   Sofosbuvir /            • Sofosbuvir (400 mg):         1 tablet PO once     • 12-Week duration for all patients
   Velpatasvir               NS5B Nucleotide Polymerase   daily WITHOUT        • Safe and approved in decompensated
   (Epclusa)                 Inhibitor                    regard to food for     cirrhosis (Child-Pugh B/C; + ribavirin)
                           • Velpatasvir (100 mg):        12 WEEKS             • Gastric pH Interaction: Velpatasvir
                             NS5A Inhibitor                                      requires acid for absorption. Avoid high-
                                                                                 dose PPIs! Max omeprazole 20 mg given
                                                                                 4 hrs AFTER velpatasvir with food
                                                                               • Amiodarone Contraindication: Fatal
                                                                                 bradyarrhythmias reported with sofosbuvir
   ═════════════════════════════════════════════════════════════════════════════════════════════════════════════

Definition of Cure: Sustained Virologic Response at 12 Weeks (SVR12)

Virologic cure is defined as achieving a Sustained Virologic Response at 12 weeks post-treatment (SVR12), demonstrated by an undetectable quantitative HCV RNA level 12 weeks after completing DAA therapy. Achieving SVR12 is associated with profound long-term clinical benefits: >70% reduction in hepatocellular carcinoma risk, >80% reduction in liver-related mortality, and improvement in extrahepatic manifestations (e.g., resolution of mixed cryoglobulinemic vasculitis and improved glycemic control).

Post-SVR Long-Term Clinical Surveillance Protocol

Achieving virologic cure clears the infection, but management following SVR12 depends entirely upon the patient's pre-treatment hepatic fibrosis stage:

                     POST-SVR SURVEILLANCE RECOMMENDATIONS

   Pre-Treatment Fibrosis Stage   Long-Term Clinical Management & Surveillance Protocol
   ═════════════════════════════════════════════════════════════════════════════════════════════
   Non-Advanced Fibrosis          • CONSIDERED COMPLETELY CURED
   (Stages F0, F1, or F2)         • No ongoing hepatology follow-up or liver imaging required
                                  • No routine serial HCV RNA testing unless reinfection is
                                    suspected due to persistent risk behaviors (e.g., active IVDU)
                                  • Note: Anti-HCV antibodies remain positive for life and
                                    do not confer protective immunity; reinfection is possible

   Advanced Fibrosis (Stage F3)   • MANDATORY LIFELONG HCC SURVEILLANCE
   or Cirrhosis (Stage F4)        • Abdominal Ultrasound with or without serum AFP every 6 months
                                  • Rationale: Although SVR12 significantly lowers the relative risk
                                    of HCC, the absolute annual risk remains >1% to 2% per year
                                    due to pre-existing genetic alterations in cirrhotic nodules
                                  • Ongoing clinical surveillance for portal hypertension complications
                                    and annual screening for esophageal varices (if indicated)
   ═════════════════════════════════════════════════════════════════════════════════════════════