What are the recommended pre and post infusion lab tests for patients receiving Rituxan (rituximab) therapy?

Pre and Post Lab Testing for Rituxan (Rituximab) Infusion

All patients must undergo hepatitis B screening (HBsAg, anti-HBc, and anti-HBs) before initiating rituximab, as this medication carries the highest risk of HBV reactivation among all immunosuppressive agents, and complete blood counts should be obtained before the first dose and monitored regularly throughout treatment. 1, 2

Pre-Infusion Laboratory Testing (Mandatory)

Hepatitis B Virus Screening

• Screen all patients for HBV infection by measuring HBsAg, anti-HBc, and anti-HBs before the first rituximab dose, as rituximab carries a >10% risk of HBV reactivation and can cause fulminant hepatitis, liver failure, and death. 1, 2
• For HBsAg-positive patients (HBV carriers): Measure baseline HBV DNA levels and refer urgently to a hepatologist for antiviral prophylaxis with entecavir, tenofovir, or tenofovir alafenamide (TAF) before starting rituximab. 2
• For HBsAg-negative but anti-HBc-positive patients (resolved HBV): Measure baseline HBV DNA, as these patients are at high risk (>10%) for reactivation with rituximab and require antiviral prophylaxis regardless of DNA levels. 2
• The reactivation risk with rituximab is 50-64% without prophylaxis and continues for up to 2 years after treatment completion, making this the single most critical pre-treatment screening. 3

Hepatitis C Virus Screening

• Screen for HCV with anti-HCV antibodies in patients with elevated ALT or known risk factors (intravenous drug use, blood transfusions). 2
• If anti-HCV antibodies are positive, measure HCV-RNA levels and refer for antiviral treatment consideration. 2

Complete Blood Count and Baseline Hematology

• Obtain CBC with differential and platelet count prior to the first rituximab dose to establish baseline values. 1
• This is essential as rituximab causes B-cell depletion and can lead to cytopenias requiring monitoring. 1

Additional Pre-Treatment Screening

• Screen for tuberculosis using interferon-gamma release assay (IGRA) or tuberculin skin test before initiating rituximab. 4, 2
• Measure baseline immunoglobulin levels (IgG), as levels <3 g/L predict higher risk of secondary immunodeficiency and severe infections. 4, 5
• Screen for HIV in high-risk patients or according to institutional protocols. 2

During Treatment Monitoring

Hepatitis B Monitoring

• For HBsAg-positive patients on antiviral prophylaxis: Monitor HBV DNA and liver function tests (ALT, AST, bilirubin) every 3-6 months during rituximab therapy and for at least 18 months after the last dose. 2
• For anti-HBc-positive patients: Monitor HBV DNA and/or HBsAg every 1-3 months during treatment and for at least 12 months after completion, as HBsAg seroreversion can occur and lead to severe hepatitis. 2
• Continue antiviral prophylaxis for at least 18 months after stopping rituximab-based regimens, as late reactivation is common. 2

Hematologic Monitoring

• For lymphoid malignancies: Obtain CBC with differential and platelet counts prior to each rituximab course during monotherapy. 1
• When rituximab is combined with chemotherapy: Obtain CBC with differential and platelets at weekly to monthly intervals, with more frequent monitoring in patients who develop cytopenias. 1
• For rheumatologic conditions (RA, GPA, MPA): Obtain CBC with differential and platelets at 2-4 month intervals during therapy. 1

Immunoglobulin Monitoring

• Monitor serum immunoglobulin levels periodically during treatment, as hypogammaglobulinemia risk increases with multiple courses and predisposes to serious infections. 5

Post-Infusion Monitoring

Immediate Post-Infusion (Same Day)

• Monitor vital signs and observe for infusion-related reactions during and for at least 30-60 minutes after completing each infusion. 1
• Watch for signs of cytokine release syndrome (fever, rigors, chills, hypotension) or severe reactions (bronchospasm, hypoxia, respiratory distress). 6, 5

Extended Post-Treatment Monitoring

• Continue CBC monitoring after the final dose until cytopenias resolve, as B-cell depletion persists with median recovery time of 9 months (range 5.9-14.4 months). 1, 5
• Continue HBV monitoring for at least 12-18 months after rituximab completion in all patients with positive HBV serology, as late reactivation is well-documented. 2
• Monitor for signs of progressive multifocal leukoencephalopathy (PML) including new neurological symptoms, as this is a potentially fatal complication. 5

Critical Pitfalls to Avoid

• Never start rituximab without HBV screening, as studies show only 23-79% of patients receive adequate screening in practice, leading to preventable deaths from fulminant hepatitis. 7, 8, 9
• Do not rely on risk factor assessment alone for HBV screening—universal screening is mandatory as 57% of patients requiring prophylaxis have no recognized HBV risk factors. 7
• Do not use lamivudine for HBV prophylaxis due to high resistance rates; use entecavir, tenofovir, or TAF instead. 2
• Do not stop antiviral prophylaxis early—continue for at least 18 months after rituximab completion, as most reactivations occur after drug discontinuation. 2
• Consider Pneumocystis jiroveci prophylaxis (trimethoprim-sulfamethoxazole) in patients receiving concomitant immunosuppression, as infection risk is significantly elevated. 2, 4