What laboratory and infection screening tests are required before initiating infliximab therapy?

Pre-Treatment Testing Before Initiating Infliximab

Before starting infliximab, you must screen for tuberculosis (TB) and hepatitis B virus (HBV) infection at minimum—these are mandatory tests required by FDA labeling and clinical guidelines. 1

Mandatory Infection Screening

Tuberculosis Screening

• Test for latent TB infection using either:
  • Tuberculin skin test (TST), OR
  • Interferon-gamma release assay (IGRA)
• Chest X-ray to evaluate for active tuberculosis
• Consider a positive result if TST induration ≥5 mm, even in patients previously vaccinated with BCG 1
• Initiate anti-TB therapy before infliximab if:
  • Latent TB is detected
  • Past history of TB without confirmed adequate treatment
  • Negative test but TB risk factors present (travel to endemic areas, close TB contact)

The FDA label explicitly states that tuberculosis reactivation is a serious risk, and treatment of latent TB prior to infliximab has been shown to reduce reactivation risk 1. A tuberculin skin test induration of 5 mm or greater should trigger treatment consideration, which is a lower threshold than standard TB screening.

Hepatitis B Screening

• Test for HBV exposure/infection before initiating therapy 2, 3
• The AGA guidelines specifically mention hepatitis B screening as part of pretreatment workup for all biologic therapies 2
• Antiviral treatment should be started in HBsAg-positive patients at the time of infliximab initiation 3

Additional Infection Considerations

• Rule out active infections before starting therapy—infliximab should not be initiated in patients with any active infection, including clinically important localized infections 1
• Consider HIV testing in appropriate risk populations 3
• Varicella zoster virus (VZV) antibody testing if prior infection history is uncertain 3

Additional Laboratory Tests

Baseline Laboratory Monitoring

While not explicitly mandated by FDA labeling for pre-treatment, the following are recommended:

• Complete blood count (CBC)
• Liver function tests (LFTs)
• Basic metabolic panel

These establish baseline values for ongoing monitoring during therapy, as routine monitoring of CBC and LFTs is recommended once treatment begins 4.

Disease-Specific Testing

• Confirm active inflammation before initiating therapy using:
  • Disease-related symptoms
  • Biomarkers (CRP, fecal calprotectin)
  • Endoscopic evaluation 2

Cardiovascular and Other Assessments

Cardiac Evaluation

• Clinical assessment for heart failure is critical—infliximab at doses >5 mg/kg is contraindicated in moderate-to-severe heart failure (NYHA Class III/IV) 1
• Physical examination should include heart auscultation 3

Malignancy History

• Assess for prior malignancies—cases of malignant disease within 5 years of starting anti-TNF therapy require careful consideration 3
• Lymph node examination should be performed 3

Geographic Risk Assessment

Evaluate whether the patient:

• Has resided or traveled in areas endemic for tuberculosis or mycoses (histoplasmosis, coccidioidomycosis, blastomycosis)
• Has history of opportunistic infections
• Has chronic or recurrent infections 1

Vaccination Status Review

Before starting infliximab, consider updating vaccinations (must use inactivated vaccines only):

• Pneumococcal vaccine (23-valent)
• Annual influenza vaccine
• Herpes zoster vaccine (particularly important before starting immunosuppression)
• HBV vaccination in seronegative patients
• HPV vaccination per national guidelines 3

Common Pitfalls to Avoid

1. Don't skip TB screening—this is the most critical pre-treatment test and reactivation can be fatal
2. Don't use live vaccines once immunosuppression has started
3. Don't ignore travel history—patients from or traveling to TB/fungal endemic areas need extra scrutiny
4. Don't start infliximab with any active infection present—even seemingly minor localized infections are contraindications
5. Don't forget that older patients (>65 years) and those on concomitant immunosuppressants have higher infection risk and may need more intensive screening 1

Summary Algorithm

Minimum required tests:

1. TB screening (TST or IGRA) + chest X-ray
2. Hepatitis B serology
3. Rule out active infections clinically
4. Cardiac assessment (history/exam for heart failure)

Strongly recommended additional tests: 5. CBC, LFTs, basic metabolic panel 6. HIV testing (if risk factors present) 7. VZV serology (if history uncertain) 8. Confirm active inflammatory disease 9. Review vaccination status