5 Steps and What To Expect

Asthma is diagnosed through a medical history, physical exam, and lung function tests. A pulmonologist, who specializes in the respiratory system, can diagnose and help manage asthma.

The diagnostic criteria for asthma are based on the assessment of symptoms, medical history, physical exam, and lung function tests. The most commonly criteria are the Global Initiative for Asthma (GINA) criteria.

The GINA criteria assess four main aspects, which include:

• Airway hyperresponsiveness: Hyperresponsive airways narrow excessively in response to triggers. Bronchial challenge tests measure airway sensitivity.
• Documented variation in lung function: Asthma causes variations in lung function. Breathing worsens due to triggers. Lung function tests may be repeated to detect these changes.
• Exclusion of alternative diagnoses: A healthcare provider will rule out conditions with similar symptoms, such as heart failure or chronic obstructive pulmonary disease (COPD).
• Symptoms: Coughing, wheezing, dyspnea (shortness of breath), and chest tightness vary in severity and over time.

A careful review of your medical history can provide important clues to help diagnose asthma.

A healthcare provider will consider factors to rule out or diagnose asthma, such as:

• Environmental exposures: A healthcare provider will ask about exposure to lung irritants and allergens at home and work.
• Family history: The risk of asthma is higher in people with a family history of asthma or allergies.
• Symptoms: A healthcare provider will ask about your symptoms, when they started, how often they occur, how long they last, and what triggers them.
• Medical conditions: Some past or current conditions may increase the risk of asthma or mimic its symptoms.
• Medication use: Some medications can worsen asthma symptoms, such as beta-blockers or non-steroidal anti-inflammatories (NSAIDs).

During a physical exam, a healthcare provider will listen to your lungs while you breathe. They will assess your respiratory rate and look for signs of rapid or shallow breathing.

A healthcare provider may place a pulse oximeter on your finger to measure your blood oxygen levels.

Pulmonary (lung) function tests measure different aspects of your respiratory health to confirm or rule out asthma.

Spirometry

Spirometry is a non-invasive test that measures how much air you can breathe in and out of your lungs and how quickly. 

You will be asked to take a deep breath and exhale forcefully and quickly into a spirometer machine. 

Spirometry results include: 

• Forced expiratory volume (FEV1): The amount of air you can blow out in the first second (lower than average may indicate asthma)
• Forced vital capacity (FVC): The amount of air you can blow out after taking a deep breath

These numbers can help calculate your FEV1/FVC ratio. This represents the percentage of your lung capacity you can exhale in 1 second. For children, the FEV1/FVC ratio is low if it is less than 85%. For adults, the equivalent is less than 70%.

Peak Flow Meter

A peak flow meter is a handheld device that measures the maximum airflow rate you can achieve during a forceful exhale. You will take a deep breath and forcefully exhale into the device.

The scores are separated into three “zones,” which include:

• Green (80-100% of your usual peak flow rate): Asthma is currently controlled
• Yellow (50-80% of your usual peak flow rate): In the cautionary range, which requires appropriate treatment
• Red (50% or less of your usual peak flow rate): In the medical alert range, which needs immediate medical attention

For best results, regularly test your peak flow so you have a good understanding of your baseline.

FeNO Test

A fractional exhaled nitric oxide (FeNO) test measures the exhaled level of nitric oxide (NO) in your breath. NO is a marker of a specific time of airway inflammation.

You will exhale slowly and steadily into a device.

This test helps diagnose eosinophilic asthma. This subtype is characterized by high levels of eosinophils (a type of white blood cell).

Bronchial Provocation Tests

A bronchial provocation test, or methacholine challenge test, sees how reactive or sensitive your airways are.

A healthcare provider will ask you to breathe into a spirometer to get a baseline result. Then, you will be given a small dose of methacholine, which narrows the airways.

The spirometer test will be repeated to measure how your airways respond to the methacholine. A 20% or more reduction in breathing ability means your airways are reactive, which can signal asthma.

A healthcare provider may recommend allergy testing if they suspect allergies trigger your symptoms.

Common allergy tests include:

• Immunoglobulin E (IgE) test: This blood test measures the amount of IgE, or antibodies the immune system makes in response to allergens. High levels can indicate an allergy to airborne allergens that may trigger asthma symptoms.
• Skin prick test: A small amount of an allergen is placed on your skin, which is scratched to allow it in. Redness, swelling, or itching can indicate an allergy.

A healthcare provider may order an imaging test to rule out other conditions that cause similar symptoms. They might include a chest X-ray, acid reflux test, or sinus imaging.

Imaging tests can also diagnose asthma in young children who cannot reliably perform lung function tests.

A healthcare provider must rule out other conditions that can cause similar symptoms, such as:

• Bronchiectasis
• Congestive heart failure (CHF)
• COPD
• Gastroesophageal reflux disease (GERD)
• Vocal cord dysfunction (VCD)

Conditions that are common in people with asthma include:

• Allergies 
• Anxiety and depression
• Obesity 
• Obstructive sleep apnea 
• Rhinitis, or swelling of the nose

To diagnose asthma, a healthcare provider will evaluate your symptoms, medical history, and lung function tests. 

A healthcare provider must rule out other conditions that mimic asthma, such as COPD and bronchiectasis. They can also screen for related conditions like allergies, GERD, and obstructive sleep apnea.