Sofie Wise

Bryan Welch

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About Author — Bryan is a Philly transplant living in West Hollywood. When not performing with his band, he's writing, obsessing over movies, or building art. Bryan also enjoys regular rowing & healthy cooking.

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Asthma Diagnosis: How Do You Test for Asthma?

Asthma is a chronic respiratory condition that affects millions in the Unites States every day. Not only does it affect the daily lives of those afflicted, it can also be deadly if ignored or untreated. While a higher percentage of asthma cases develop in early adolescence, a large portion of the adult population suffers from asthma. According to a 2015 report by the CDC, 24.6 million Americans suffer from asthma, including 8.4% of all children and 7.6% of adults. The Global Initiative for Asthma defines it as “a chronic inflammatory disorder of the airways in which many cells and cellular elements play a role.” While only a doctor can diagnose asthma accurately, there is still much uncertainty in the field of asthma studies. How can we know what it is, and how do we diagnose asthma? First we must gain a practical knowledge of what asthma is, then we will be better able to understand the methods of diagnosis. So, what are we working with?

Understanding Asthma

Asthma is a chronic inflammatory disease affecting the bronchus, or airway of the respiratory tract leading to the lungs. The presence of asthma is determined by a combination of genetic and environmental stimuli. However, the exact cause of asthma is not known with certainty. What is known with certainty is that asthma is incurable. Symptoms can be mitigated by usage of corticosteroids (usually via inhaler), and by avoiding or responding to known asthma triggers, such as dust, pollen, pollution, smoking, and heavy exercise. Though attacks can be prevented to some degree, it is ultimately a lifelong disease that can be onset at any age.
Asthma symptoms are typically characterized by coughing, wheezing, shortness of breath, and bronchial spasms. Let’s see how a doctor might diagnose these symptoms.

Methods of Asthma Diagnosis

As there is no agreed upon definition of asthma, there are no precise guidelines for the diagnosis and management of asthma. This is not to say that diagnoses are not to be 100% trustworthy, but rather that similar conclusions can be met by various methods. Most diagnoses are based upon symptomatic patterns and therapeutic response, and hold more weight when the patient has exhibited a history of coughing, wheezing, and difficulty breathing. These symptoms are even more conclusive if they are found to be more extreme when exposed to common environmental asthmatic stimuli, like dust, air pollution, cold air, and exercise.

How do you test for asthma? Upon examination of these symptoms and the patient’s history, a doctor will likely confirm their diagnosis by way of spirometry.


Spirometry comes from the roots “spiro” (breath) and “metre” (measure), so spirometry is the measurement of breath. The most common test using spirometry is the FEV-1 or the forced expiration by volume for 1 second. Healthy lungs should be able to output anywhere from 80-120% of their expected expiration (based on variables like age, sex, race, etc.). For those with asthma, that percentage will be far lower.

The way that doctors actually confirm the presence of asthma is by giving the test first, without the aid of steroids or other medicines. They then immediately administer a bronchodilator and redo the test. A bronchodilator is used as a quick relief medication to open airways. If the post-inhalant result is 12% higher and the output is more than 200 milliliters more than the original, it is a good indication that the patient does indeed have asthma. In those with a history of mild asthma who are not currently exhibiting symptoms during the test, results may not be as conclusive. Spirometry can also be used to monitor the efficacy of the patient’s treatment throughout the years.

Bronchial Challenge Test

Another asthma test that has proven useful is the bronchial challenge test, also known as the methacholine test or the histamine test. This test uses the same concept of comparing spirometry readings, but uses a negative stimulus instead of a positive. The doctor will expose the patient to methacholine or histamine, which will intentionally constrict the bronchioles. After the initial test, the doctor will likely introduce a bronchodilator such as salbutamol in order to judge whether the patient is suffering from asthma or chronic obstructive pulmonary disorder (COPD). This test is called a post bronchodilator test or PB. The readings are then compared and used to determine if and to what degree the patient is suffering from asthma.

Though useful, the bronchial challenge test has been know to provide false positives, as even non asthmatic participants may have significant trouble breathing after exposure to these stimuli. However, negative readings are a reliable way to rule out asthma in the patient.

Other Methods

Another method to diagnose asthma is prescribing a bronchodilator such as salbutamol or corticosteroids and gauging the peak expiratory flow (PEF) of the patient throughout the weeks following. If the patient sees a 20% increase in PEF on at least 3 days of the week for at least 2 weeks, it is likely that they have asthma. Similar results may be found in response to known asthmatic triggers. If the PEF is negatively affected by 20% or more, it is also likely that the patient has asthma. These tests are used for diagnostic confirmation and measurement of therapeutic response.

The Asthma Control Test.

The asthma control test (ACT) is an questionnaire designed to evaluate the severity of an individual’s asthma, and to gauge how well treatment is working. It is self-administered and brought to a physician’s attention in order to work out a management plan. The ACT does not measure spirometry, but rather allows the patient to evaluate how asthma affects his or her activities in their daily life. It consists of five questions, which the patient then marks from one to five, one being on the generally negative side of the question, and five indicating control.
Those who score a 5 on the ACT have almost no control of their asthma, while those with 25 have almost total control. The ACT is used mostly as a benchmark upon which to base your clinical needs.

Classifying Asthma Type

Given the many different potential triggers and the nebulous nature of asthma’s definition, it should come as no surprise that there are many types of asthma on the doctor’s radar. Classification takes into account frequency and severity as well as the triggers that may set off an asthma attack.

The level of severity is usually measured by way of spirometry and frequency of acute exacerbations (asthma attacks). Here is a look at those classifications.

  • Intermittent
    * Symptoms occur two or less times per week
    * Nighttime symptoms occur two or less times per month
    * Inhaler used two or less days per week
  • Mild Persistent
    * Symptoms occur more than twice per week
    * Nighttime symptoms occur three to four times per month
    * Inhaler used more than two days per week
  • Moderate Persistent
    * Symptoms occur daily
    * Nighttime symptoms more than once per week
    * Inhaler used daily
  • Severe Persistent
    * Symptoms occur continuously
    * Nighttime symptoms nightly
    * Inhaler used twice daily

Then, there’s classifying the severity of the asthma attacks themselves, which is done by examining both the spirometry and the symptomatic aspects of each acute exacerbation. They are classified as follows:

  • Mild Exacerbation
    * May see mild coughing and wheezing, minor chest tightness
  • Moderate Exacerbation
    * Heavier wheezing and coughing
    * Shortness of breath
    * Difficulty completing sentences in one breath
  • Severe Exacerbation
    * "Silent chest” or not enough air passing through airways fast enough to produce wheezing
    * Chest pain
    * Coughing fits
    * Exhaustion
    * Cyanosis
    * Arrhythmia
    * Altered state of mind
  • Acute Severe Exacerbation
    * Acute severe exacerbations do not respond to regular treatment such as inhalers and corticosteroids, and are mostly atopic attacks
    * Heart rate above 110 BPM
    * Difficulty speaking
  • Brittle Asthma
    * Type 1: Recurrent severe attacks
    * Type 2: Well controlled, moderate asthma interspersed with recurrent severe attacks

Other Classifications

Asthma is currently separated into atopic and non-atopic categories. Atopic asthma is asthma that is believed to stem from preexisting allergies, while non-atopic asthma is spurred by other stimuli. While these are the only two clinical subgroups, there are many categories of asthma.

  • Exercise-Induced Asthma – Most asthmatic individuals will see an increase in their symptoms during exercise, and up to 20% of non-asthmatic people experience a form of bronchodilation during exercise. This is mostly seen in endurance sports, such as swimming, rowing, cycling, and XC skiing as well as being most common in cold, dry weather.
  • Aspirin-Induced Asthma – This affects at least 9% of asthmatic individuals and accompanies most NSAIDs such as aspirin and ibuprofen. Typical symptoms can be accompanied by:
    * Runny nose
    * Inflamed nasal passage
    * Gastrointestinal stress
    * Hives
  • Alcohol-Induced Asthma – Primarily found in those of Asian descent, alcohol-induced asthma is characterized by:
    * Bronchoconstriction
    * Hives
    * Rapid heart rate
    * Dizziness
    * Inflated nasal passages
    * In rare cases, sufferers may experience anaphylaxis, cardiovascular collapse, or even death
  • Occupational Asthma – Asthma that is exacerbated by fumes, dust, and conditions in the workplace. Nearly 5-25% of all adult asthma cases are believed to be occupational asthma. Commonly afflicted occupations include:
    * Animal workers
    * Bakers
    * Granary workers
    * Welders
    * Construction workers
    * Factory workers who use latex gloves
    * Carpenters
    * Nurses
    * Painters

Asthma can be tricky to pin down, but with careful attention and medical evaluation, a diagnosis can be reached.

Do you think you have asthma? Learn about symptoms, causes, or information on asthma treatment and medication.

If you think you have symptoms of asthma, call or book online with PlushCare to set up a phone appointment with a top U.S. doctor today.


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