What is the diagnostic approach for asthma?

From the Guidelines

The diagnostic approach for asthma involves a comprehensive evaluation of symptoms, medical history, physical examination, and objective testing, with spirometry being essential for diagnosis, as recommended by the most recent guidelines 1.

Key Diagnostic Steps

• Clinicians should first assess for characteristic symptoms including wheezing, shortness of breath, chest tightness, and cough that vary over time and in intensity.
• A detailed medical history should be taken, including questions about symptoms, triggers, and previous diagnoses, as outlined in the expert panel report 3 (EPR-3) guidelines 1.
• Physical examination may reveal findings that increase the probability of asthma, but the absence of these findings does not rule out asthma.
• Spirometry is essential for diagnosis, with a positive result showing airflow limitation and bronchodilator reversibility, as defined by an improvement in FEV1 of at least 12% and 200mL after inhaling a short-acting beta-agonist.

Additional Diagnostic Tests

• When spirometry is normal but asthma is still suspected, additional tests may be necessary, such as:
  • Bronchial challenge testing with methacholine
  • Exercise challenge
  • Peak expiratory flow (PEF) monitoring over 2-4 weeks, with PEF variability exceeding 10% in adults or 13% in children suggesting asthma
  • Fractional exhaled nitric oxide (FeNO) measurement to identify eosinophilic airway inflammation, with levels above 50 ppb in adults supporting an asthma diagnosis
• Chest X-rays are not diagnostic but help exclude alternative conditions.

Diagnostic Algorithm

• The European Respiratory Society clinical practice guidelines for the diagnosis of asthma in children aged 5-16 years recommend a diagnostic algorithm that includes two positive, evidence-based tests to confirm the diagnosis 1.
• The algorithm includes spirometry, BDR testing, and FeNO as the most widely available objective tests.

Reference Standard

• In the absence of a universally accepted reference standard for the diagnosis of asthma, a "doctor diagnosis of asthma" supported by at least one abnormal comparator test is accepted as the standard 1.
• The comparator tests include spirometry, BDR, FeNO, 2-week peak expiratory flow rate (PEFR) variability test, direct and indirect bronchial challenge tests.

From the FDA Drug Label

The FDA drug label does not answer the question.

From the Research

Diagnostic Approach for Asthma

The diagnostic approach for asthma involves a combination of clinical assessment, medical history, physical examination, and diagnostic testing.

• Clinical assessment: Patients with asthma present with symptoms such as cough, dyspnea, and wheezing 2.
• Medical history: Symptoms such as wheezing, chest tightness, and difficulty in taking a deep breath suggest asthma, while symptoms such as gasping, smothering, or air hunger suggest alternative diagnoses 3.
• Physical examination: The physical exam can demonstrate hyperinflation, wheezing, and increased work of breathing, but most patients will present with a normal pulmonary exam because they are between episodes 2.

Diagnostic Testing

Diagnostic testing for asthma includes:

• Spirometry with bronchodilator reversibility testing: This remains the mainstay of asthma diagnostic testing for children and adults 4.
• Repeated peak flow measurement: This is relatively simple to implement in a clinical and home setting 4.
• Bronchial challenge testing: This is reserved for patients in whom the aforementioned testing has been unrevealing but clinical suspicion remains, though it is associated with low specificity 4.
• Fractional exhaled nitric oxide measurement: This may be supportive of atopic asthma, though diagnostic utility is limited particularly in non-atopic asthma 4, 5, 6.

Predictors of Asthma Diagnosis and Treatment Response

• Airway reversibility in bronchodilation tests and fractional exhaled nitric oxide can predict the response to anti-asthma therapy in patients with suspected asthma 5.
• ΔFEV1% in bronchodilation tests together with FeNO predicted a positive response to anti-asthma therapy and an asthma diagnosis in patients with a normal FEV1 and negative bronchodilation test 5.
• FeNO levels increased significantly after albuterol inhalation in steroid-naive asthmatics but not in ICS-treated asthmatics or COPD patients, supporting the role of FeNO in differentiating asthmatics from COPD patients with positive bronchodilator test 6.