What is the diagnostic approach for adult asthma?

From the Guidelines

The diagnostic approach for adult asthma involves a comprehensive evaluation of symptoms, medical history, physical examination, and objective testing, with spirometry being essential for diagnosis, as indicated by the most recent and highest quality study 1. The diagnostic process should start with assessing characteristic symptoms, including wheezing, shortness of breath, chest tightness, and cough that vary over time and in intensity. A detailed history should document symptom patterns, triggers, family history of asthma or allergies, and response to previous treatments.

• Key symptoms to consider include:
  • Cough, particularly at night
  • Recurrent wheeze
  • Recurrent difficulty in breathing
  • Recurrent chest tightness
• Symptoms may occur or worsen in the presence of specific triggers, such as:
  • Exercise
  • Viral infection
  • Inhalant allergens
  • Irritants
  • Changes in weather
  • Strong emotional expression
  • Stress
  • Menstrual cycles Physical examination may reveal wheezing on auscultation, though findings can be normal between exacerbations.
• The physical examination should focus on:
  • The upper respiratory tract
  • The chest
  • The skin Spirometry is crucial for diagnosis, with a positive test showing airflow obstruction (FEV1/FVC ratio <0.7) that improves by at least 12% and 200mL after bronchodilator administration, as supported by 1 and 1. If spirometry is normal but asthma is still suspected, additional tests include bronchial challenge testing with methacholine, exercise challenge, or peak flow monitoring showing diurnal variability >10%, as mentioned in 1. Fractional exhaled nitric oxide (FeNO) measurement can help identify eosinophilic airway inflammation, with values >50 ppb supporting an asthma diagnosis. Allergy testing may identify specific triggers, and chest imaging is typically normal in asthma but helps exclude alternative diagnoses. Differential diagnoses to consider include COPD, vocal cord dysfunction, heart failure, and bronchiectasis, as discussed in 1 and 1. The diagnostic approach should be thorough, as misdiagnosis can lead to inappropriate treatment and poor symptom control, emphasizing the importance of a comprehensive evaluation as outlined in the most recent guideline 1.

From the FDA Drug Label

Provocholine, used in a methacholine challenge test, is indicated for the diagnosis of bronchial airway hyperreactivity in adults and pediatric patients five years of age and older who do not have clinically apparent asthma. The diagnostic approach for adult asthma involves a methacholine challenge test to assess bronchial airway hyperreactivity.

• Key steps in the diagnostic approach include:
  • Baseline spirometry to ensure FEV1 is greater than or equal to 60% of the predicted value and greater than or equal to 1.5 L in adults.
  • Administration of Provocholine via nebulization using either the 5-Breath Dosimeter Dosing Method or the 2-Minute Tidal Breathing Dosing Method.
  • Calculation and interpretation of methacholine challenge test results, with a positive test indicated by a reduction in FEV1 of 20% or more from post-diluent FEV1 2. The methacholine challenge test is not recommended for patients with clinically apparent asthma or wheezing 2 2.

From the Research

Diagnostic Approach for Adult Asthma

The diagnostic approach for adult asthma involves a combination of clinical assessment, physical examination, and diagnostic testing. The following are the key steps involved in diagnosing adult asthma:

• Clinical assessment: A thorough history of symptoms, such as cough, wheeze, breathlessness, and chest tightness, is essential in diagnosing asthma 3, 4.
• 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 4.
• Diagnostic testing: Spirometry is a crucial diagnostic test for asthma, and a large bronchodilator response makes asthma more likely 5. However, normal spirometry is common in patients with mild asthma who are not symptomatic at the time of testing.
• Additional tests: Inhalation challenge test, such as a methacholine inhalation test, can help confirm asthma in patients with normal spirometry 5, 6.
• Differentiation from other conditions: Adult smokers with intermittent respiratory symptoms may have either asthma or chronic obstructive pulmonary disease (COPD), and normal post-bronchodilator spirometry rules out COPD 5.

Diagnostic Challenges

Diagnosing asthma can be challenging, especially in patients with normal spirometry or those who are not symptomatic at the time of testing. The following are some of the diagnostic challenges:

• Normal spirometry: Patients with mild asthma may have normal spirometry, making it essential to rely on clinical assessment and other diagnostic tests 5, 7.
• Similar symptoms: Asthma symptoms can be similar to those of other conditions, such as COPD, making it essential to use a combination of diagnostic tests to confirm the diagnosis 5.
• Variability of symptoms: Asthma symptoms can vary greatly from patient to patient and within the same patient over time, making it essential to monitor symptoms and adjust treatment accordingly 4.