As a rural family physician, where can I refer an adult patient with suspected asthma for formal pulmonary function testing including pre‑ and post‑bronchodilator spirometry?

Where to Refer for Pulmonary Function Testing in Rural Practice

Refer your patient to the nearest facility capable of performing formal spirometry with pre- and post-bronchodilator testing—this may be a pulmonology clinic, allergy/immunology practice, hospital-based pulmonary function laboratory, or even a well-equipped primary care office with trained personnel and quality-controlled spirometry equipment. 1, 2

Specific Referral Options

Primary Referral Targets

• Pulmonology or allergy/immunology specialty clinics are the most reliable destinations, as specialists are significantly more likely to perform spirometry than general practitioners (only 25% of patients report undergoing pulmonary function tests in primary care offices versus higher rates with specialists). 1

• Hospital-based pulmonary function laboratories can perform comprehensive testing including spirometry, flow-volume loops, lung volumes, diffusing capacity, and bronchial challenge testing if needed. 1

• Tertiary care centers or academic medical centers often have dedicated pulmonary function labs with trained respiratory therapists who can ensure quality-controlled, guideline-compliant testing. 1

What Testing Must Be Performed

The referral site must be capable of:

• Pre- and post-bronchodilator spirometry to demonstrate reversible airflow obstruction (≥12% and ≥200 mL improvement in FEV₁ after bronchodilator). 1, 2, 3

• Flow-volume loops to assess for alternative diagnoses like vocal cord dysfunction. 1

• If initial spirometry is normal but clinical suspicion remains high, the facility should offer methacholine or histamine bronchial challenge testing to demonstrate airway hyperresponsiveness. 1, 4, 5

Alternative Options When Specialty Referral Is Not Accessible

In-Office Spirometry

• High-quality office-based spirometry performed by trained staff with proper equipment can provide diagnostic information as reliable as hospital-based testing. 5

• You must ensure your office spirometer meets quality standards, staff are trained in proper technique, and results meet acceptability and reproducibility criteria before interpretation. 6

• Office spirometry is appropriate for initial diagnostic testing but may require referral for bronchial challenge testing if spirometry is normal and suspicion persists. 5, 7

Peak Flow Monitoring (Limited Diagnostic Role)

• Peak flow meters should NOT be used as a primary diagnostic tool—they are intended for monitoring established asthma, not diagnosis. 2

• However, if formal spirometry is completely unavailable, 2-week home peak flow monitoring showing ≥20% diurnal variation with ≥60 L/min change can support the diagnosis when combined with typical symptoms. 3, 4

Critical Timing Considerations

• Testing must be performed within 24 hours of symptoms or workplace exposure (if occupational asthma is suspected), as airway hyperresponsiveness may normalize with longer periods away from triggers, leading to false-negative results. 1

• Baseline spirometry may be completely normal between episodes of bronchospasm, so a single normal test does not exclude asthma—this is when bronchial challenge testing becomes essential. 3, 4

Common Pitfalls to Avoid

• Do not rely on symptoms alone for diagnosis—objective spirometry is mandatory in patients ≥5 years old. 2, 4

• Do not accept "clinical diagnosis" without objective testing—studies show 33% of patients with physician-diagnosed asthma have no objective evidence of disease on formal testing, and up to 45% of pediatric patients with parent-reported asthma are overdiagnosed. 1

• Do not assume all wheezing is asthma—the referral site must systematically exclude COPD, vocal cord dysfunction, cardiac disease, and other mimics. 2, 4

Practical Approach for Rural Settings

1. Identify the nearest facility (within reasonable driving distance) that performs quality-controlled spirometry with bronchodilator testing—call ahead to confirm they follow ATS/ERS guidelines. 1

2. If no specialty clinic exists within 50–100 miles, consider establishing in-office spirometry capability with proper training and equipment, but maintain a referral pathway for bronchial challenge testing when needed. 5

3. For patients who cannot travel, telemedicine consultation with a pulmonologist or allergist may help guide diagnosis, though objective testing will still require in-person evaluation at some point. 1

4. Document the specific indication in your referral (e.g., "suspected asthma, need spirometry with bronchodilator response and possible methacholine challenge if spirometry normal") to ensure appropriate testing is performed. 1, 4