What are the criteria for significant reversibility on spirometry?

Criteria for Significant Reversibility on Spirometry

Significant reversibility on spirometry is defined as an increase in FEV1 that is both greater than 200 mL AND a 15% increase over the pre-bronchodilator value. 1

Standard Reversibility Testing Protocol

Preparation

• Test should be performed when patients are clinically stable and free from infection
• Patients should withhold medications prior to testing:
  • Short-acting bronchodilators: 6 hours
  • Long-acting β-agonists: 12 hours
  • Sustained-release theophyllines: 24 hours
  • Smoking: avoid for 1 hour prior and throughout testing 1

Administration Method

1. Perform baseline spirometry with three acceptable tests
2. Administer bronchodilator medication:
   • Salbutamol/albuterol: 2.5-5 mg nebulized (wait 15 minutes)
   • Ipratropium bromide: 500 μg nebulized (wait 30 minutes)
   • Or both in combination (wait 30 minutes) 1

Interpretation

• Primary criterion: FEV1 increase >200 mL AND >15% from baseline 1
• Alternative criterion used in some settings: FEV1 increase ≥12% AND ≥200 mL 2

Clinical Significance of Reversibility Testing

Diagnostic Value

• Helps differentiate between asthma and COPD
• Establishes post-bronchodilator FEV1 as a prognostic indicator
• A response of ≥200 mL in FEV1 after steroids suggests better prognosis over five years 1

Important Considerations

• A negative FEV1 response does not preclude clinical benefit from bronchodilators in terms of:
  • Improved walking distance
  • Reduced perception of breathlessness 1
• FVC improvement may be more sensitive than FEV1 in detecting bronchodilator response in severe COPD 3

Special Populations

Children

• In children with chronic respiratory symptoms, a decrease in airway resistance (Rrs0) of 27.8% has been associated with significant reversibility 1
• For children under 7 years, a 41% decrease in Rrs5 exceeds the 95% confidence interval for normal bronchodilator response 1

Common Pitfalls

1. Overlooking FVC improvements: In severe COPD, FVC may show greater improvement than FEV1 after bronchodilator administration 3

2. Testing patients with very normal spirometry: Patients with pre-bronchodilator FEV1 >100% of predicted have extremely low probability of positive bronchodilator response (0%) 4

3. Misinterpreting restrictive patterns: Some patients with restrictive spirometry may show bronchodilator responsiveness due to air trapping from early airway closure 5

4. Using fixed cutoffs across all age groups: Using a fixed FEV1/FVC ratio of 0.70 can lead to false-positive diagnoses in older adults and false-negative diagnoses in younger adults 6

Corticosteroid Reversibility Testing

When bronchodilator testing is negative but clinical suspicion remains high:

• Administer oral prednisolone (30 mg daily) for two weeks, or
• Inhaled steroid (e.g., beclomethasone 500 μg twice daily) for six weeks
• Same criteria apply: FEV1 increase >200 mL AND >15% from baseline 1
• Alternative: 20% rise in mean PEF (measured over first five days vs last five days of steroid course) 1

By following these standardized criteria and protocols for spirometric reversibility testing, clinicians can more accurately diagnose and manage patients with obstructive airway diseases, leading to improved outcomes in terms of morbidity, mortality, and quality of life.