Introduction: Who Should Undergo Diagnostics

If you or your child experience symptoms such as wheezing, coughing, shortness of breath, or chest tightness, it’s important to see a doctor. These signs may appear only at certain times, such as during exercise or at night, or they may be present most of the time. Asthma can start in childhood, but it can also develop when you are an adult.^[1][2]

You should seek medical advice if breathing problems interfere with your daily activities, wake you up at night, or become worse after physical activity or at certain times of the year. Sometimes these symptoms might seem mild at first, but they can worsen over time. Early diagnosis helps prevent serious complications and allows you to manage your condition effectively.^[7][8]

Children who wheeze frequently and have repeated respiratory infections that continue beyond the age of six are at greater risk of developing asthma. If you have a family history of asthma, allergies, or eczema, or if you were exposed to toxins, fumes, or smoke early in life, you may also be at higher risk. In these cases, it is advisable to discuss your symptoms with a healthcare provider sooner rather than later.^[1][6]

Even if you feel fine between episodes, it is still important to undergo diagnostic testing. Asthma symptoms can come and go, and what seems like occasional trouble breathing might actually be a chronic condition that needs ongoing management. Proper diagnosis ensures you receive the right treatment and avoid potentially life-threatening asthma attacks.^[5]

Diagnostic Methods

Diagnosing asthma involves a combination of discussing your symptoms, reviewing your medical history, performing a physical examination, and conducting specific tests. Because asthma symptoms can vary over time and resemble other conditions, doctors use multiple approaches to confirm the diagnosis.^[1][10]

Medical History and Physical Examination

Your doctor will start by asking detailed questions about your symptoms. They will want to know when your symptoms occur, what makes them worse, and whether anything helps you feel better. They may ask if you cough frequently, especially at night, or if you experience breathing problems after physical activity or during certain seasons. Your doctor will also inquire about your family history, as having parents or siblings with asthma or allergies increases your risk.^[1][8]

During the physical exam, the doctor will listen to your chest with a stethoscope. This helps them detect wheezing or other abnormal sounds that suggest narrowed airways. They will also check for signs of other conditions, such as respiratory infections or chronic obstructive pulmonary disease (COPD), which is a long-term lung disease that can cause similar symptoms. Ruling out other possible causes is an important part of diagnosing asthma.^[10]

Lung Function Tests

Lung function tests are the most important tools for diagnosing asthma. These tests measure how much air you can breathe in and out, and how fast you can do so. They help doctors understand how well your lungs are working and whether your airways are narrowed.^[1][10]

Spirometry is the most common lung function test. During this test, you take a deep breath and then exhale as hard and fast as you can into a device called a spirometer. The device measures the amount of air you breathe out and how quickly you can do it. This helps doctors estimate how narrow your airways are. If your airways are narrowed, it suggests asthma.^[10]

Often, spirometry is performed both before and after you use a medication called a bronchodilator, which opens up the airways. If your lung function improves after using the bronchodilator, it is a strong sign that you have asthma. This improvement shows that your airways can respond to treatment, which is a key feature of asthma.^[1][10]

Another test is the peak flow meter, a simple handheld device that measures how hard you can breathe out. Your doctor may give you a peak flow meter to use at home for a few weeks. You record your results over time, and lower readings can indicate that your asthma is getting worse or that your lungs are not working as well. This tool helps track your condition and can provide early warning of an asthma attack.^[10][16]

Additional Tests

If the diagnosis is still unclear after lung function tests, your doctor may recommend additional tests to confirm asthma or identify triggers.^[10]

A methacholine challenge test involves inhaling a substance called methacholine, which is known to trigger asthma symptoms. If you react to methacholine by experiencing narrowed airways, it is likely you have asthma. This test may be used even if your initial lung function test results are normal.^[10]

Allergy testing can help identify whether allergies are triggering your asthma symptoms. Allergies to pets, dust mites, pollen, or mold are common asthma triggers. Allergy tests can be performed as a skin test, where small amounts of allergens are applied to your skin, or as a blood test. Knowing your specific allergens helps you avoid them and manage your asthma more effectively.^[1][10]

Imaging tests, such as a chest X-ray, may be used to rule out other conditions that can cause breathing problems, such as infections or structural abnormalities in the lungs. While a chest X-ray does not diagnose asthma directly, it helps doctors ensure that your symptoms are not caused by something else.^[10]

A blood count may be ordered to look at the level of certain white blood cells called eosinophils. High levels of eosinophils can indicate inflammation in the airways, which is common in people with asthma. Blood tests may also check for other markers of inflammation.^[1]

Specialized Tests

In some cases, doctors may use more specialized tests. A FeNO test, which stands for fractional exhaled nitric oxide, measures the amount of nitric oxide in your breath. High levels of nitric oxide indicate inflammation in the airways, which is a sign of asthma. This test is simple and painless, and involves breathing into a device for a few seconds.^[4]

Provocation tests may also be used. These tests involve exposing you to substances that commonly trigger asthma, such as cold air or exercise, to see if your airways react. These tests are done in a controlled medical setting to ensure your safety.^[4]

Diagnostics for Clinical Trial Qualification

When patients are being considered for enrollment in clinical trials, more detailed and standardized diagnostic tests may be required. Clinical trials often have strict criteria to ensure that participants truly have asthma and that the trial results are accurate.^[15]

Most clinical trials require confirmation of asthma through spirometry. Participants must demonstrate a certain level of airway obstruction or show improvement in lung function after using a bronchodilator. These measurements help researchers classify the severity of asthma and ensure that all participants have comparable conditions.^[15]

Trials studying severe asthma may also require blood tests to measure eosinophil levels or other markers of inflammation. For example, some biologic medications are designed for patients with high eosinophil counts, so trial participants must meet specific blood count criteria. Blood eosinophil counts of 300 cells per microliter or higher are often used as a threshold for these studies.^[15]

Allergy testing may also be required for trials studying allergic asthma. Participants may need to demonstrate sensitivity to specific allergens through skin prick tests or blood tests. This ensures that the trial is studying the right group of patients and that the treatment being tested is appropriate for their type of asthma.^[15]

Asthma control questionnaires, such as the Asthma Control Test, may be used to assess how well a person’s asthma is controlled before they enter a trial. These questionnaires ask about symptoms, medication use, and how asthma affects daily life. Participants with poorly controlled asthma may be eligible for trials testing new treatments aimed at improving control.^[15]

Some trials may also require participants to track their symptoms and peak flow readings at home for a period of time before enrollment. This helps researchers understand the baseline severity and variability of each participant’s asthma. Detailed records of asthma attacks, medication use, and symptom patterns provide valuable information for the trial.^[15]

In trials studying new biologic medications, additional tests may be required to measure specific immune markers or proteins in the blood. These tests help identify which patients are most likely to benefit from the experimental treatment. For instance, trials for biologic drugs targeting specific immune pathways may require measurement of immunoglobulin E (IgE) levels or other immune system markers.^[15]

Overall, diagnostic testing for clinical trial qualification is more rigorous and detailed than standard diagnostic testing. This ensures that trial results are reliable and that new treatments are tested on the appropriate patient populations. If you are considering joining a clinical trial, be prepared for thorough testing and detailed documentation of your asthma history and current condition.