What workup is recommended before administering mepolizumab (anti-IL-5 therapy)?

Workup Before Mepolizumab Administration

Before administering mepolizumab, a complete blood count with differential to assess eosinophil levels is the most essential laboratory test required. 1 This baseline assessment is critical as mepolizumab specifically targets IL-5, which is responsible for eosinophil maturation and survival.

Essential Pre-Treatment Evaluations

Laboratory Testing

• Complete blood count with differential - to document baseline eosinophil count
• Inflammatory markers - ESR and CRP to assess baseline inflammation 1
• Liver function tests - to ensure no contraindications to therapy 1
• Screening for chronic infections:
  • Tuberculosis screening (TB test) prior to initiating therapy 1
  • Hepatitis B and C screening 1

Disease-Specific Assessments

For patients with specific conditions requiring mepolizumab:

For Eosinophilic Asthma:

• Pulmonary function tests - baseline FEV1/FVC 1
• Asthma Control Test (ACT) score 2
• Peak Nasal Inspiratory Flow (PNIF) if nasal symptoms present 1

For Chronic Rhinosinusitis with Nasal Polyps:

• Endoscopic polyp score (0-8 scale) 1
• VAS symptom scores for rhinorrhea, mucus, nasal blockage, loss of smell 1
• SNOT-22 questionnaire to assess sinonasal symptoms 1, 3

For Eosinophilic Granulomatosis with Polyangiitis (EGPA):

• ANCA testing - particularly MPO-ANCA 1
• Cardiac evaluation - including troponin and echocardiogram to rule out cardiac involvement 1
• Neurologic examination - to document any baseline neuropathy 1
• Renal function tests - to assess for renal involvement 1

Specialized Testing for EGPA (when diagnosis is uncertain)

• Electromyography (EMG) 1
• MRI of affected areas 1
• Muscle biopsy if myositis is suspected 1
• Autoimmune myositis panel 1
• Paraneoplastic autoantibody testing 1

Documentation Requirements

Before initiating mepolizumab therapy, document:

1. Previous treatments and their efficacy
2. Exacerbation history (frequency and severity)
3. Current oral corticosteroid dose (if applicable) 1
4. Baseline quality of life measurements

Contraindications and Precautions

• Hypersensitivity to mepolizumab or any excipients
• Active helminth infections should be treated before initiating therapy
• Pregnancy status should be determined in women of childbearing potential

Follow-up Monitoring Plan

Document a plan for monitoring treatment response:

• Reassessment of eosinophil counts after 4-8 weeks
• Evaluation of clinical response at 8-12 weeks 1
• Assessment of steroid-sparing effect 2

Common Pitfalls to Avoid

1. Failure to establish baseline eosinophil count - Essential for documenting response
2. Not screening for latent infections - TB reactivation is a risk with immunomodulatory therapy
3. Inadequate assessment of organ involvement in EGPA - cardiac, pulmonary, and neurological evaluations are critical
4. Not documenting baseline corticosteroid requirements - Important for assessing steroid-sparing effect
5. Overlooking comorbid conditions that may affect treatment response

Mepolizumab is generally well-tolerated, with adverse events comparable to placebo in clinical trials 1. However, proper pre-treatment evaluation ensures appropriate patient selection and establishes important baseline parameters for monitoring treatment efficacy.