What is the definition and treatment of reactive airway disease in adults?

Reactive Airway Disease in Adults: Definition and Management

"Reactive airway disease" (RAD) is not a formally recognized diagnostic term in current medical guidelines and should be avoided in adult patients—instead, clinicians must establish a specific diagnosis such as asthma, cough variant asthma, eosinophilic bronchitis, or reactive airways dysfunction syndrome (RADS).

Understanding the Term "Reactive Airway Disease"

The term "reactive airway disease" is a non-specific descriptor that has been used historically to describe respiratory conditions characterized by wheezing, bronchial hyperresponsiveness, and airflow obstruction, but it lacks diagnostic precision and is not endorsed by major respiratory societies 1.

What RAD Actually Represents

When clinicians use "RAD," they are typically referring to one of several distinct conditions:

• Asthma: A chronic inflammatory disorder characterized by reversible airflow obstruction, bronchial hyperresponsiveness, and recurrent episodes of wheezing, chest tightness, or coughing 2, 3
• Cough Variant Asthma (CVA): Persistent nonproductive cough as the sole manifestation of asthma, with hypersensitive cough receptors and bronchial hyperresponsiveness 4, 2
• Reactive Airways Dysfunction Syndrome (RADS): Persistent airway hyperresponsiveness following a single massive exposure to an irritant, gas, vapor, or fume 5
• Eosinophilic Bronchitis: Eosinophilic airway inflammation without airway hyperresponsiveness 6, 4

Establishing the Correct Diagnosis

Clinical Presentation to Assess

When evaluating an adult with suspected "reactive airway disease," systematically assess for:

• Episodic symptoms: Recurrent wheezing, dyspnea, chest tightness, or cough that are variable, intermittent, worse at night, and triggered by exercise or allergens 1, 7
• Isolated chronic cough: May represent cough variant asthma, which accounts for 24-29% of chronic cough cases in adult nonsmokers 4
• Exposure history: Single high-level irritant exposure suggests RADS, while repeated exposures may cause chronic airway hyperresponsiveness 5

Diagnostic Testing Algorithm

Step 1: Spirometry with Bronchodilator Testing

• Perform spirometry to document variable expiratory airflow limitation—this is mandatory to establish asthma diagnosis objectively 7
• A positive bronchodilator response (FEV1 improvement ≥12% and ≥200 mL) confirms reversible airflow obstruction 1, 7

Step 2: Bronchial Challenge Testing (if spirometry normal)

• Methacholine challenge testing demonstrates airway hyperresponsiveness when physical examination and spirometry are non-diagnostic 4, 2
• A negative methacholine test essentially excludes asthma due to very high negative predictive power 4
• This distinguishes cough variant asthma (positive test) from non-asthmatic eosinophilic bronchitis (negative test) 6

Step 3: Assess Eosinophilic Inflammation

• Measure sputum eosinophil counts (>3% is diagnostic of eosinophilic inflammation) or fractional exhaled nitric oxide (FeNO) to predict corticosteroid responsiveness 6, 4
• Blood eosinophils ≥150 cells/μL suggest eosinophilic asthma 1

Treatment Approach Based on Specific Diagnosis

For Asthma (Including Cough Variant Asthma)

First-Line Treatment:

• Initiate inhaled corticosteroids (ICS) immediately upon diagnosis—this is the cornerstone of therapy 6
• Start with low to medium doses (beclomethasone 200-800 μg daily equivalent) using twice-daily dosing with proper inhaler technique 6
• For cough variant asthma specifically, add an inhaled bronchodilator to the ICS regimen 6

Stepwise Escalation for Inadequate Response:

• Week 4-8: If cough or symptoms persist, increase ICS dose up to 2000 μg beclomethasone daily equivalent 6
• Add leukotriene receptor antagonist (montelukast) if response remains inadequate—there is specific evidence supporting this combination in cough variant asthma 6
• Short-course oral corticosteroids: Reserve prednisolone 30 mg daily for 1-2 weeks only for severe/refractory cases after maximizing inhaled therapy 6

For Eosinophilic Bronchitis (Without Airway Hyperresponsiveness)

• Treat with ICS as first-line therapy using the same stepwise approach as asthma 6
• A 2-week trial of oral prednisolone 30 mg daily can establish diagnosis if cough resolves 6
• Note: Long-acting beta-agonists are not indicated, as there is no airway hyperresponsiveness 6

For Reactive Airways Dysfunction Syndrome (RADS)

• Manage similarly to asthma with ICS and bronchodilators, as RADS presents with persistent airway hyperresponsiveness 5
• Document the single high-level irritant exposure in the history 5

Critical Pitfalls to Avoid

• Do not use "reactive airway disease" as a final diagnosis—it delays appropriate treatment and fails to guide long-term management 1
• Do not prescribe oral corticosteroids before trying ICS—this violates guideline-based stepwise therapy 6
• Do not assume normal spirometry excludes asthma—bronchial challenge testing is required when clinical suspicion is high 4, 7
• Do not overlook alternative diagnoses: Exclude GERD, ACE inhibitor-induced cough, upper airway cough syndrome, COPD, and heart failure before finalizing asthma diagnosis 6, 7

Monitoring Treatment Response

• Assess response to ICS within 4-8 weeks using symptom control and quality of life measures 6
• For eosinophilic inflammation, repeat sputum eosinophil counts after 2-4 weeks—expect 50-70% reduction with effective treatment 4
• If no response after 2 weeks of oral prednisolone trial, cough is unlikely due to eosinophilic airway inflammation and alternative diagnoses must be reconsidered 6

Long-Term Considerations

• Approximately 30% of patients with cough variant asthma may develop typical asthma symptoms within several years if inadequately treated 4
• Chronic anti-inflammatory therapy is appropriate given the presence of airway remodeling and subepithelial layer thickening in these conditions 6, 4
• Sputum-guided therapy reduces exacerbations by up to 60% in patients with eosinophilic inflammation 4