Diagnosing Asthma
The diagnostic process of asthma depends on a person’s age, symptoms, and overall health.
Factors That Can make diagnosis difficult
- Asthma symptoms can mimic other diseases, such as respiratory infections.
- Symptoms do not always appear daily and may only occur at night or during specific triggers.
- A symptom-free period during a doctor’s visit may result in a normal physical exam, making diagnosis harder.
- Some diagnostic tests are difficult to perform in young children, elderly individuals, or those with certain medical conditions.
Steps in Diagnosing Asthma
Physical Examination
Doctors check for signs of chronic respiratory issues, like:
- difficulty breathing and shortness of breath
- chronic cough
- wheezing
They also rule out other possible causes like specific respiratory infections.
Pulmonary Function Tests
Pulmonary function tests are usually performed in children over 5 years old and in adults – doctors decide based on symptoms, age, and overall health condition.
Spirometry
- Purpose: Spirometry is used to estimate the narrowing of the bronchial tubes, the airways in your lungs. It measures how well the lungs function by checking how much air a person can exhale after taking a deep breath and how fast they can exhale.
- Asthma indicator: People with asthma usually have lower results than those with healthy lungs.
Bronchoprovocation Testing
- Purpose: Assesses lung response to specific provocation/triggers like cold air or exercise.
- Asthma Indicator: If a person’s lung function drops significantly after exposure, it may indicate asthma
Exhaled Nitric Oxide
- Purpose: Helps determine airway inflammation, especially when spirometry results are inconclusive (unclear).
- Asthma indicator: Higher-than-normal nitric oxide levels suggest airway inflammation
Peak Flow Measurement
- Purpose: It is more a monitoring than diagnostic tool and used to determine the severity of the asthma.
- Asthma Indicator: Measures how hard a person can breathe out (exhale). Values lower than your personal best may indicate worsening of asthma symptoms.
Allergy Testing
Doctors may also test for allergies to identify potential asthma triggers. Common testing methods are skin prick test and blood test. Food allergy testing is usually unnecessary unless symptoms include gastrointestinal (GI) symptoms or other signs strongly linked to asthma.
Additional Testing
If asthma symptoms don’t improve with standard treatment or another health condition is suspected, doctors may recommend further tests, including:
- Chest X-ray – to rule out other lung conditions
- Modified barium swallow – if aspiration is suspected
- Sweat chloride test: used in newborns (2 weeks and older) if Cystic Fibrosis (CF) is suspected
- Sputum eosinophils test: examines cells in your mucus to assess asthma severity and treatment success
- Metacholine challenge test: metacholine is used to provoke airway narrowing. A positive test suggests asthma
Asthma Severity Levels
Once diagnosed, asthma can further be categorized by severity:
- Mild intermittent (symptoms 1-2 days/week; up to 2 nights/month)
- Mild persistent (symptoms >2 days/week; not more than 1x/day)
- Moderated persistent (symptoms daily; more than 1 night/week)
- Severe persistent (symptoms throughout the day on most days; frequently also at night)