What is the next best step in evaluating a 20-year-old male college student with a three-week history of episodic cough and dyspnea worse in the mornings, allergic rhinitis, and recent syncope?

Next Best Step: Spirometry with Bronchodilator Testing

The next best step is to perform spirometry with bronchodilator testing to confirm reversible airflow limitation and establish the diagnosis of asthma. 1

Clinical Reasoning

This 20-year-old presents with a three-week history of episodic cough and dyspnea worse in the mornings, which strongly suggests cough-variant asthma or early asthma, particularly given his history of allergic rhinitis. 1 The syncope episode requires urgent evaluation but does not change the primary respiratory diagnostic approach—it may represent vasovagal response to severe coughing paroxysms or requires separate cardiac workup if concerning features are present.

Why Spirometry is the Correct Next Step

• At the three-week mark, this patient's cough has reached the threshold where distinguishing transient bronchial hyperresponsiveness from true asthma becomes clinically important. 1

• Spirometry with pre- and post-bronchodilator testing is essential to confirm reversible airflow limitation, which is the hallmark of asthma. 1, 2 The test should demonstrate FEV1 improvement ≥12% and ≥200 mL with bronchodilator to confirm significant reversibility. 3

• Cough-variant asthma should be suspected in adults with persistent cough that worsens at night or in the morning, and diagnosis relies on demonstrating bronchodilator response or positive methacholine challenge. 1, 4

• The presence of allergic rhinitis significantly increases the likelihood of asthma, as patients with allergic rhinitis are at greater risk of developing asthma and other lower airway disease. 5, 6

Why NOT Other Options

Methacholine challenge test: While this can confirm airway hyperresponsiveness, it should be reserved for patients with normal spirometry results who still have high clinical suspicion for asthma. 1 Start with basic spirometry first. 1

Empiric inhaled corticosteroids: Although ICS are first-line treatment for confirmed asthma 1, 2, prescribing without objective confirmation risks treating the wrong diagnosis and missing other serious conditions. 1 At three weeks, many patients with acute bronchitis still have transient bronchial hyperresponsiveness that will resolve spontaneously. 1

Empiric montelukast: Leukotriene inhibitors are second-line agents, considered only after ICS therapy or when ICS response is incomplete. 1 Starting with montelukast without confirming the diagnosis is inappropriate.

Systemic steroids: There is no indication for systemic corticosteroids in this stable outpatient with three weeks of symptoms and no evidence of severe airflow obstruction. 1

Diagnostic Algorithm

1. Perform spirometry with pre- and post-bronchodilator testing immediately 1, 2

   • Measure FEV1, FVC, and FEV1/FVC ratio before and 15-20 minutes after bronchodilator administration
   • Significant reversibility = FEV1 improvement ≥12% and ≥200 mL 3

2. If spirometry shows reversible airflow limitation:

   • Diagnose asthma and initiate ICS as first-line controller therapy 1, 2
   • Add short-acting beta-agonist for symptom relief 2
   • Consider step-up therapy with leukotriene inhibitor if response to ICS is incomplete 1

3. If spirometry is normal but clinical suspicion remains high:

   • Consider methacholine challenge testing to confirm airway hyperresponsiveness 1
   • PC20 <2 mg/mL confirms diagnosis of cough-variant asthma 1

4. If cough persists beyond 8 weeks despite treatment:

   • Reclassify as chronic cough and initiate systematic evaluation 4
   • Consider other diagnoses including vocal cord dysfunction, gastroesophageal reflux, or non-asthmatic eosinophilic bronchitis 1

Critical Pitfalls to Avoid

• Do not assume this is simple acute bronchitis at three weeks. While transient bronchial hyperresponsiveness can persist for 2-3 weeks after acute bronchitis, symptoms lasting ≥3 weeks warrant evaluation for chronic conditions like asthma. 1, 4

• Do not prescribe bronchodilators or ICS empirically without objective testing. The diagnosis of asthma requires documentation of reversible airflow limitation or airway hyperresponsiveness. 1, 2

• Do not ignore the syncope. While focusing on the respiratory diagnosis, ensure appropriate evaluation of the syncopal episode, particularly if it occurred independent of coughing paroxysms. 1

• Do not order chest radiography at this stage unless pneumonia is suspected. With normal vital signs and no focal chest findings, chest X-ray is not indicated at three weeks. 1, 4