What are the different classifications of asthma and how are they determined?

Asthma Classification Systems

Asthma severity is classified into four main categories: intermittent, mild persistent, moderate persistent, and severe persistent, based on both impairment and risk domains. 1

Primary Classification System

The National Asthma Education and Prevention Program (NAEPP) classification divides asthma severity into four groups:

1. Intermittent Asthma

• Symptoms: ≤2 days per week
• Nighttime awakenings: ≤2 times per month
• SABA use for symptom control: ≤2 days per week
• Interference with normal activity: None
• Lung function: FEV₁ ≥80% predicted, FEV₁/FVC normal
• Risk: 0-1 exacerbation requiring oral corticosteroids per year

2. Mild Persistent Asthma

• Symptoms: >2 days per week, but not daily
• Nighttime awakenings: 3-4 times per month
• SABA use: >2 days per week, but not more than once per day
• Interference with normal activity: Minor limitation
• Lung function: FEV₁ ≥80% predicted, FEV₁/FVC reduced >5%
• Risk: ≥2 exacerbations requiring oral corticosteroids per year

3. Moderate Persistent Asthma

• Symptoms: Daily
• Nighttime awakenings: >Once per week, but not nightly
• SABA use: Daily
• Interference with normal activity: Some limitation
• Lung function: FEV₁ 60-80% predicted, FEV₁/FVC reduced >5%
• Risk: ≥2 exacerbations requiring oral corticosteroids per year

4. Severe Persistent Asthma

• Symptoms: Throughout the day
• Nighttime awakenings: Often 7 times per week
• SABA use: Several times per day
• Interference with normal activity: Extremely limited
• Lung function: FEV₁ <60% predicted
• Risk: ≥2 exacerbations requiring oral corticosteroids per year 1, 2

Assessment Domains

1. Impairment Domain

Impairment refers to the frequency and intensity of symptoms and functional limitations experienced by the patient:

• Daytime symptoms
• Nighttime awakenings
• Need for rescue medication (short-acting beta-agonists)
• Ability to perform normal activities
• Lung function measurements (FEV₁, PEF)

2. Risk Domain

Risk refers to the likelihood of future adverse events:

• Frequency of exacerbations requiring oral systemic corticosteroids
• Progressive loss of lung function
• Risk of medication side effects 1, 2

How to Classify Asthma Severity

1. For Initial Assessment (Treatment-Naïve Patients):

   • Assess both impairment and risk domains
   • Classify based on the most severe category in which any feature occurs
   • Use spirometry to objectively measure lung function

2. For Follow-up Assessments:

   • Focus on asthma control rather than severity
   • Categorize as "well controlled," "not well controlled," or "very poorly controlled"
   • Adjust therapy based on level of control 1

Important Considerations in Classification

• Severity is ideally determined before initiating therapy 1
• Once treatment begins, the focus shifts to assessing control rather than severity 3
• Asthma severity is not a fixed feature and may change over months or years 3
• Patients with ≥2 exacerbations requiring oral corticosteroids in the last year should be considered as having persistent asthma, regardless of their level of functional impairment 2
• Spirometry is critical for diagnosis and classification, not just peak flow measurements 1

Risk Factors for Potentially Fatal Asthma

The following factors indicate higher risk for asthma-related mortality:

• Previous intubation or ICU admission for asthma
• ≥2 hospitalizations for asthma in the last year
• ≥3 emergency department visits for asthma in the last year
• Hospitalization or emergency department visit in the last month
• Use of >2 short-acting beta-agonist inhalers per month
• Difficulty perceiving symptoms or severity of exacerbations 2

Common Pitfalls in Classification

• Underestimating severity: Patients often underestimate their symptoms, leading to incorrect classification 1
• Not considering activity level: Studies show that when activity level is included in classification, many patients classified as having mild asthma actually have moderate to severe asthma 1
• Relying solely on lung function: FEV₁ and PEF do not always correlate with symptom severity; more than 25% of patients with normal lung function may still have subsequent asthma attacks 1
• Failing to recognize that mild asthma can lead to severe exacerbations: Severe exacerbations in mild asthma represent 30-40% of asthma exacerbations requiring emergency consultation 4

Remember that classification should guide initial treatment decisions, but ongoing management should focus on achieving and maintaining asthma control through regular assessment and appropriate adjustment of therapy.