Asthma Diagnosis: Current Guidelines
For diagnosing asthma, establish the diagnosis through medical history and physical examination documenting recurrent episodes of airflow obstruction, then confirm with spirometry in all patients ≥5 years of age demonstrating at least partially reversible airway obstruction. 1
Diagnostic Approach
Clinical Assessment
The diagnosis begins with identifying specific symptoms that indicate recurrent airflow obstruction:
- Wheezing (particularly at night or early morning)
- Cough (especially nocturnal or early morning)
- Breathlessness
- Chest tightness
These symptoms should be variable and episodic, often triggered by specific exposures (allergens, irritants, exercise, cold air, viral infections). 1
Objective Confirmation with Spirometry
Spirometry is mandatory for all patients ≥5 years of age to objectively confirm airway obstruction and reversibility. 1 This is critical because:
- Demonstrates airflow limitation (reduced FEV1/FVC ratio)
- Proves reversibility (≥12% and ≥200 mL improvement in FEV1 after bronchodilator)
- Rules out alternative diagnoses
For patients with normal or near-normal spirometry but suspected asthma, bronchoprovocation testing (methacholine, histamine, cold air, or exercise challenge) can identify airway hyperresponsiveness. A positive test supports asthma diagnosis, while a negative test effectively rules it out. 1
Diagnostic Challenges to Avoid
Cough-variant asthma: Cough may be the only manifestation, especially in young children. Diagnosis is confirmed by positive response to asthma medications. 1
Vocal cord dysfunction (VCD): Can mimic asthma but requires different treatment. Look for variable flattening of the inspiratory flow loop on spirometry. Consider VCD in patients with difficult-to-treat, atypical asthma unresponsive to standard therapy. 1
Children ages 0-4 years: Diagnosis is challenging without objective lung function testing. Avoid labels like "wheezy bronchitis" or "reactive airway disease" that delay appropriate asthma treatment. Consider referral to a specialist if diagnosis is uncertain. 1
Alternative Diagnoses to Exclude
Before confirming asthma, rule out:
In children:
- Foreign body aspiration
- Vocal cord dysfunction
- Vascular rings or laryngeal webs
- Recurrent aspiration from GERD
In adults:
- COPD (chronic bronchitis/emphysema)
- Congestive heart failure
- Pulmonary embolism
- Drug-induced cough (ACE inhibitors)
- Mechanical airway obstruction (tumors) 1
Initial Severity Classification
Once asthma is diagnosed, classify severity before initiating therapy using both impairment and risk domains:
Impairment domain:
- Symptom frequency (daytime and nighttime)
- SABA use for symptom relief
- Interference with normal activity
- Lung function (FEV1 or PEF)
Risk domain:
- Frequency of exacerbations requiring oral corticosteroids
- History of ICU admissions or intubations 1
This severity classification determines the initial treatment step (1-6), with intermittent asthma starting at step 1 and severe persistent asthma requiring steps 5-6.
Updated Recommendations from 2020 Guidelines
The 2020 NAEPP update 2 introduced important changes:
- Step 2 (mild persistent asthma): Either daily low-dose ICS plus as-needed SABA OR as-needed concomitant ICS and SABA therapy (not just as-needed SABA alone)
- Fractional exhaled nitric oxide (FeNO) testing: Recommended to assist in diagnosis and monitoring, but not as a standalone diagnostic tool
- Spirometry remains the gold standard for objective confirmation
Key Pitfalls
- Never diagnose asthma on symptoms alone without objective testing in patients ≥5 years
- Don't miss VCD in patients with atypical presentations or poor response to therapy
- Avoid underdiagnosing young children by using vague labels instead of treating appropriately
- Consider comorbidities (GERD, OSA, rhinitis, obesity) that complicate diagnosis and management 1