Diagnosis of Persistent Asthma
Persistent asthma is diagnosed when symptoms occur more than twice weekly, with specific patterns of impairment in both symptom frequency and lung function measurements that exceed those seen in intermittent asthma. 1
Classification Criteria for Persistent Asthma
Persistent asthma is categorized into three levels of severity based on both impairment and risk domains:
1. Mild Persistent Asthma
- Symptoms: >2 days/week but not daily
- Nighttime awakenings: 3-4 times/month
- SABA use: >2 days/week but not daily
- Activity limitation: Minor limitation
- Lung function: FEV₁ ≥80% predicted; FEV₁/FVC normal
- Exacerbations: ≥2/year requiring oral corticosteroids 1
2. Moderate Persistent Asthma
- Symptoms: Daily
- Nighttime awakenings: >1/week but not nightly
- SABA use: Daily
- Activity limitation: Some limitation
- Lung function: FEV₁ >60% but <80% predicted; FEV₁/FVC reduced >5%
- Exacerbations: ≥2/year requiring oral corticosteroids 1
3. Severe Persistent Asthma
- Symptoms: Throughout the day
- Nighttime awakenings: Often 7 times/week
- SABA use: Several times per day
- Activity limitation: Extremely limited
- Lung function: FEV₁ <60% predicted; FEV₁/FVC reduced >5%
- Exacerbations: ≥2/year requiring oral corticosteroids 1
Important Diagnostic Considerations
Risk Domain Assessment
Even if a patient has symptoms consistent with intermittent asthma, they should be classified as having persistent asthma if they've had ≥2 exacerbations requiring oral corticosteroids in the past year. This critical point ensures proper treatment intensity. 1
Objective Testing
- Spirometry is essential for initial diagnosis and should be performed at least every 1-2 years after treatment initiation 1
- Reversibility testing: A post-bronchodilator improvement in FEV₁ of ≥12% and ≥200 mL confirms asthma diagnosis 2
- Peak flow variability: Variation of ≥20% establishes a definite diagnosis of asthma 3
Validated Questionnaires
Several questionnaires can help assess symptom control:
- Asthma Control Test (ACT)
- Asthma Control Questionnaire (ACQ)
- Asthma Therapy Assessment Questionnaire (ATAQ) 1
Common Pitfalls in Diagnosis
Misdiagnosis: Failing to differentiate asthma from COPD, vocal cord dysfunction, or other respiratory conditions 4
Overlooking comorbidities: Untreated GERD, rhinosinusitis, or obesity can mimic or worsen asthma symptoms 5
Inadequate assessment of adherence: Poor medication adherence may be mistaken for severe disease 5
Insufficient objective testing: Relying solely on symptoms without spirometry leads to misclassification 2
Missing exacerbation history: Patients with ≥2 exacerbations requiring oral corticosteroids should be classified as having persistent asthma regardless of symptom frequency 1
Treatment Implications
The diagnosis of persistent asthma has important treatment implications:
- All patients with persistent asthma require daily long-term control medications, particularly inhaled corticosteroids 1
- Mild persistent: Low-dose inhaled corticosteroids
- Moderate persistent: Low to medium-dose inhaled corticosteroids plus long-acting β2-agonist
- Severe persistent: High-dose inhaled corticosteroids plus long-acting β2-agonist; may require biologics or oral corticosteroids 1
Remember that asthma severity can change over time, requiring ongoing assessment of control and adjustment of therapy. The goal is to achieve and maintain control with the lowest effective medication dose.