What are the criteria for diagnosing an asthma exacerbation in a patient?

Asthma Exacerbation Diagnostic Criteria

An asthma exacerbation is diagnosed when a patient demonstrates changes in symptoms, increased rescue bronchodilator use, and decreased lung function that fall outside their usual day-to-day variation, requiring immediate severity classification and treatment initiation within 15-30 minutes. 1

Core Diagnostic Components

The diagnosis requires identifying three key elements simultaneously:

• Symptom deterioration beyond the patient's normal range of variation, including increased dyspnea, chest tightness, coughing, or wheezing 2, 1
• Increased rescue medication use exceeding the patient's baseline short-acting beta-agonist requirements 2
• Objective lung function decline documented by peak expiratory flow (PEF) or FEV₁ measurements 2, 1

Critical point: The exacerbation must represent a change from the patient's individual baseline, not just absolute values, since clinical characteristics causing distress in one patient may represent another patient's usual status 2

Severity Classification System

Once diagnosed, immediately classify severity using objective measures:

Mild Exacerbation

• PEF ≥70% of predicted or personal best 2, 1
• Dyspnea only with activity 2
• Usually managed at home with prompt relief from inhaled short-acting beta-agonist 2
• May require short course of oral systemic corticosteroids 2

Moderate Exacerbation

• PEF 40-69% of predicted or personal best 2, 1
• Dyspnea interferes with or limits usual activity 2
• Requires office or emergency department visit 2
• Needs frequent inhaled short-acting beta-agonist and oral systemic corticosteroids 2
• Symptoms persist 1-2 days after treatment initiation 2

Severe Exacerbation

• PEF <40% of predicted or personal best 2, 1
• Dyspnea at rest, interferes with conversation 2
• Requires emergency department visit and likely hospitalization 2
• Only partial relief from frequently inhaled short-acting beta-agonist 2
• Oral systemic corticosteroids required, with symptoms lasting >3 days after treatment 2
• Adjunctive therapies are helpful 2

Life-Threatening (Subset of Severe)

• PEF <25-33% of predicted or personal best 2, 1
• Too dyspneic to speak, perspiring 2
• Silent chest, altered mental status, cyanosis, or feeble respiratory effort 1
• Requires emergency department/hospitalization, possible intensive care unit 2
• Minimal or no relief from frequent inhaled short-acting beta-agonist 2
• Intravenous corticosteroids required 2

Standardized Definitions for Clinical Trials and Documentation

Severe Exacerbation (Formal Definition)

A severe exacerbation requires at least one of the following:

• Use of systemic corticosteroids (tablets, suspension, or injection), or increase from stable maintenance dose, for at least 3 days 2
• Hospitalization or emergency room visit because of asthma, requiring systemic corticosteroids 2

Important caveat: Courses of corticosteroids separated by 1 week or more should be treated as separate severe exacerbations 2

Moderate Exacerbation (Formal Definition)

• Deterioration in symptoms, lung function, and increased rescue bronchodilator use lasting 2 days or more 2
• Not severe enough to warrant systemic corticosteroid use and/or hospitalization 2
• Emergency room visits for routine sick care not requiring systemic corticosteroids may be classified as moderate 2

Note: Many exacerbations in children are treated with increased doses of inhaled corticosteroids rather than systemic corticosteroids; these should be considered moderate exacerbations until specific studies establish otherwise 2

Time Course and Pattern Recognition

Exacerbations typically follow a characteristic pattern:

• Gradual onset with PEF falling over several days, followed by more rapid changes over 2-3 days 3
• Parallel increase in symptoms and rescue beta-agonist use occurring simultaneously with PEF decline 3
• Variable speed of onset ranging from minutes/hours to 2 weeks 2
• Variable resolution time from 5 to 141 days 2

Common Pitfalls to Avoid

Do not rely solely on symptoms without objective measurement: Exacerbations identified by need for oral corticosteroids are associated with more symptoms and smaller changes in PEF than those identified by PEF criteria alone 3

Do not use PEF percentage change as the sole criterion: The inclusion of percentage change in PEF from baseline is not currently recommended as a criterion for severe exacerbations in isolation 2

Do not ignore the patient's usual variation: Absolute severity varies considerably between patients and over time, so clinical identification must be based on changes outside the patient's usual range 2

Do not delay treatment for complete assessment: Begin treatment immediately upon diagnosis while completing severity classification 1

High-Risk Features Requiring Immediate Attention

Identify patients at increased risk for asthma-related death:

• Previous severe exacerbation requiring intubation or intensive care unit admission 1
• ≥2 hospitalizations for asthma in past year 1
• ≥3 emergency department visits for asthma in past year 1
• Using >2 canisters of short-acting beta-agonist per month 1
• Difficulty perceiving asthma symptoms or severity 1

Pediatric Considerations

Special challenges in children:

• Exacerbations are frequent with significant morbidity, possibly due to frequency of viral infections 2
• No reliable methods for early detection exist, but development of upper airway symptoms of viral infection may be a useful alert 2
• Severity is difficult to characterize due to dependence on parental reporting and difficulty measuring lung function 2
• Lung function measures (FEV₁ or PEF) may be useful for children ≥5 years of age, but may not be obtainable during an exacerbation 2
• Pulse oximetry <92-94% after 1 hour is predictive of need for hospitalization 2
• Children with signs and symptoms after 1-2 hours of initial treatment who continue to meet criteria for moderate or severe exacerbation have >84% chance of requiring hospitalization 2