What is the recommended workup before initiating mepolizumab (mepolizumab) for severe asthma?

Recommended Workup Before Initiating Mepolizumab for Severe Asthma

Before initiating mepolizumab for severe asthma, patients should undergo comprehensive assessment of asthma severity, confirmation of eosinophilic phenotype with blood eosinophil count, and evaluation of current medication adherence and technique.

Confirmation of Severe Asthma Diagnosis

The first step before initiating mepolizumab is to confirm the diagnosis of severe asthma:

• Verify that the patient has persistent symptoms despite high-dose inhaled corticosteroids (ICS) plus additional controller medications
• Document poor asthma control through:
  • Frequent exacerbations requiring systemic corticosteroids
  • Reduced lung function (PEF or FEV1 <75% of predicted)
  • Poor quality of life due to asthma symptoms

Essential Laboratory and Diagnostic Tests

1. Blood eosinophil count

   • Mepolizumab specifically targets eosinophilic inflammation
   • Blood eosinophil count should be elevated (typically ≥150 cells/μL)
   • This is the most critical laboratory test as mepolizumab works by blocking interleukin-5, which is involved in eosinophil maturation and survival 1

2. Pulmonary function testing

   • Spirometry with bronchodilator reversibility
   • Document baseline FEV1 for future comparison
   • PEF measurements and diurnal variability assessment

3. Assessment of current asthma control

   • Document frequency and severity of exacerbations
   • Use validated questionnaires (e.g., Asthma Control Questionnaire)
   • Record current medication use, especially systemic corticosteroid requirements

Medication Review and Optimization

Before starting mepolizumab:

• Verify adherence to current controller medications
• Check inhaler technique
• Ensure patient has been on maximal conventional therapy including high-dose ICS plus additional controllers (typically long-acting beta-agonists)
• Document response to previous treatments

Additional Considerations

1. Exclusion of alternative diagnoses

   • Rule out conditions that can mimic severe asthma
   • Consider comorbidities that may contribute to poor asthma control 2

2. Evaluation of exacerbation history

   • Document frequency, severity, and triggers of exacerbations
   • Record emergency department visits and hospitalizations
   • Note response to previous systemic corticosteroid courses

Patient Education and Monitoring Plan

Before initiating therapy:

• Establish a self-management plan
• Provide the patient with a PEF meter if they don't already have one
• Schedule follow-up appointments (typically within 4 weeks of initiation)
• Set expectations regarding treatment response timeline

Common Pitfalls to Avoid

1. Failing to confirm eosinophilic phenotype

   • Mepolizumab specifically targets eosinophilic inflammation and is most effective in patients with elevated blood eosinophil counts
   • Without confirmation of eosinophilic phenotype, treatment may be ineffective

2. Not optimizing conventional therapy first

   • Ensure patients have truly failed conventional therapy before initiating biologics
   • Check adherence and inhaler technique as these are common causes of treatment failure

3. Overlooking comorbidities

   • Untreated comorbidities can contribute to persistent symptoms despite appropriate asthma therapy
   • Mepolizumab has shown efficacy even in patients with comorbid conditions, but these should still be addressed 2

Real-world studies have shown that mepolizumab reduces exacerbation rates by 33-48% and decreases the need for maintenance oral corticosteroids 3, 4, making it an important treatment option for appropriate patients with severe eosinophilic asthma.