Blood Work Required for Rituximab Injections
Prior to initiating rituximab, you must obtain a complete blood count (CBC) with differential and platelets, serum immunoglobulin levels (IgG, IgA, IgM), hepatitis B surface antigen (HBsAg), hepatitis B core antibody (anti-HBc), and hepatitis C antibody screening. 1
Pre-Treatment Screening (Before First Dose)
Mandatory Baseline Tests
- Complete Blood Count (CBC) with differential and platelet count is required before the first rituximab infusion 1
- Hepatitis B screening must include both HBsAg and anti-HBc measurements to detect HBV infection 1
- Serum immunoglobulin levels (IgG, IgA, IgM) should be measured at baseline, as pre-existing hypogammaglobulinemia (IgG <6 g/L) predicts increased risk of developing severe hypogammaglobulinemia and serious infections after rituximab 2, 3
Additional Screening Based on Indication
- Hepatitis C antibody screening is recommended before initiating rituximab for inflammatory myositis 4
- Latent tuberculosis screening should be performed before rituximab initiation 4
Monitoring During Rituximab Therapy
For Lymphoid Malignancies (NHL, CLL)
- CBC with differential and platelet counts prior to each rituximab course during monotherapy 1
- Weekly to monthly CBC monitoring when rituximab is combined with chemotherapy, with more frequent monitoring in patients who develop cytopenias 1
For Autoimmune Conditions (RA, GPA, MPA, Inflammatory Myositis)
- CBC with differential and platelet counts every 2-4 months during rituximab therapy 1
- Serum immunoglobulin concentrations prior to each course of rituximab to detect secondary immunodeficiency 2
- Continue monitoring for cytopenias after the final dose until resolution 1
Critical Hepatitis B Management
For Hepatitis B Core Antibody Positive Patients
- Prophylactic antiviral therapy is strongly recommended over monitoring alone when initiating rituximab in patients who are hepatitis B core antibody positive, regardless of hepatitis B surface antigen status 2
- This represents a critical safety measure to prevent hepatitis B reactivation, which can be fatal 2
Rationale for Immunoglobulin Monitoring
Pre-existing hypogammaglobulinemia (IgG <3 g/L) predicts greater risk of secondary immunodeficiency with rituximab, and baseline IgG levels correlate with post-rituximab hypogammaglobulinemia 2. In one large cohort study, 47.8% of patients had hypogammaglobulinemia before rituximab initiation, which worsened after treatment 5. Monitoring immunoglobulin levels both before and after rituximab allows for earlier identification of infection risk and patients who may benefit from immunoglobulin replacement therapy 5, 3.
Common Pitfall to Avoid
Most patients (85.4%) do not have immunoglobulin levels checked before rituximab therapy in routine practice 5. This represents a significant gap in care, as hypogammaglobulinemia is associated with increased mortality (hazard ratio 3.14-4.97 for severe infections) 5. Always measure baseline immunoglobulins—this simple test can identify high-risk patients who require closer monitoring or earlier intervention with immunoglobulin replacement therapy 5, 3.