Viral Hepatitis — Written Clinical Reasoning

SAQ 1 — HBsAg-positive patient starting R-CHOP (12 marks)

Prompt: A 61-year-old man with newly diagnosed diffuse large B-cell lymphoma is due to start R-CHOP (rituximab plus combination chemotherapy) next week. Pre-treatment screening shows HBsAg positive, total anti-HBc positive, HBeAg negative, HBV DNA 900 IU/mL and a normal ALT. Outline your assessment and your plan to prevent hepatitis B reactivation. ^[1]

Model Answer

Why this matters (3 marks):

• CDC warns that HBV reactivation can be severe and lead to death. Patients positive for both anti-HBc and HBsAg have a higher reactivation risk than those positive for anti-HBc and anti-HBs, and immunosuppressive therapy that targets B lymphocytes is a high-risk setting. ^[7]
• AASLD recommends HBsAg and anti-HBc testing in everyone before immunosuppressive, cytotoxic or immunomodulatory therapy, so this screen was the right first step. ^[1]

Prophylaxis (5 marks):

• HBsAg-positive patients should start anti-HBV prophylaxis before immunosuppressive or cytotoxic therapy. ^[1]
• Prophylaxis should start as soon as possible before, or at the latest together with, the start of immunosuppressive therapy. ^[1]
• Prefer high-barrier drugs (entecavir, TDF or TAF) over low-barrier agents. ^[1]
• Continue prophylaxis during immunosuppressive therapy and for at least 6 months after its completion, or at least 12 months for patients receiving anti-CD20 therapies. Reactivation beyond 12 months has been reported, so further monitoring should be considered, particularly after anti-CD20 antibody therapy. ^[1]

Choosing the drug (2 marks):

• Consider TAF or entecavir in patients with, or at risk of, renal dysfunction or bone disease. All nucleos(t)ide analogues except TAF need dose adjustment when creatinine clearance is below 50 mL/min. ^[1]

The resolved-infection variant (2 marks):

• If he had been HBsAg negative and anti-HBc positive, AASLD allows careful monitoring of ALT, HBV DNA and HBsAg with on-demand therapy, except for patients receiving anti-CD20 antibody therapy such as rituximab, or stem cell transplantation, for whom prophylaxis is recommended. So with R-CHOP, he would still receive prophylaxis. ^[1]
• For patients monitored without prophylaxis, HBV DNA should be checked every 1 to 3 months. ^[1]