Diagnosing asthma requires a careful health history and physical examination. Your doctor will ask about any family history of asthma or hay fever (allergic rhinitis).
Your doctor will use a stethoscope to listen for wheezing. They will also perform lung function tests (spirometry ) in children 5 years and older.
Physical Examination
As with many illnesses, your doctor will start by doing a physical exam and asking about your symptoms. He will want to know how often you experience them and if they are getting worse or better.
Your physician will also want to rule out other conditions that can cause similar symptoms, such as heart failure, chronic obstructive pulmonary disease or bronchiectasis. He will also want to know about any environmental triggers such as smoke or irritants in your home or work. Flixonase nasal spray can be used in small doses to treat asthma symptoms.
During the physical exam, your physician will ask you to breathe deeply and blow into a tube connected to a machine that measures how much air you can blow out in one second — this is called spirometry.
Your doctor will also want to know about any family history of sinusitis, rhinitis or eczema, as all of these can be associated with asthma. He will then do a complete medical history, which includes past and current health problems and your response to medications.
Lung Function Tests
Your healthcare provider may perform lung function tests (also called pulmonary function tests, or PFTs). These can help your doctor find out how well your lungs are working. They can also help your healthcare provider decide whether your asthma is mild, moderate, or severe.
One of the most important tests is called spirometry. During this test, you breathe into a tube connected to a machine that measures how much air your lungs can blow out. The machine can also measure how fast you can blow out the air. It creates a graph called a flow-volume curve, which shows how your airways are changing with time.
If your healthcare provider suspects you have asthma, they may have you do a series of repeated spirometry tests over the course of a few weeks. This way, they can see if your symptoms improve or get worse with medications and over time. They can also compare your test results to a normal population.
During spirometry, your healthcare provider might ask you to blow out as hard and quickly as you can while keeping your lips sealed around the mouthpiece. They will then record the speed, which is called your peak expiratory flow rate (PEFR).
You might also have a fractional exhaled nitric oxide (FeNO) test or bronchial provocation test, depending on the type of asthma you have.
Your healthcare provider might also order blood tests to see if you have a condition that affects your lungs, such as eosinophilia, which is common in eosinophilic asthma. They can also order blood allergy testing and a blood test to measure the amount of inflammatory markers, such as C-reactive protein, that are in your body. These can be a good indicator of inflammation in the lungs.
Allergy Tests
Allergy tests help your doctor find out which substances irritate your airways, making them swell and clog. Allergens can be found in many different things, including pollen, animal dander and mold. You can also be allergic to foods, latex and drugs. You may need to have more than one allergy test to get accurate results.
The most common allergy test is the skin prick test. During this test, your doctor will place drops of allergens on marked sections of the skin. A nurse will then use a tool called a lancet to prick the skin, just below the surface. If you are allergic to the allergen, your skin will react, forming a red bump (wheal) within 15 minutes. The nurse will measure the size of the wheal to determine which allergen you are sensitive to.
If you are taking allergy medications, like antihistamines, you should stop taking them three to seven days before your allergy test. This is because they can interfere with your test results. Your doctor will let you know what other precautions to take.
Before your allergy test, your doctor will ask you about your health history, symptoms and whether any family members have asthma or allergies. Your doctor will also want to know what seems to trigger your symptoms and when they occur. They will also want to know about your home, work and exercise habits, as these can provide clues to what’s causing your allergies.
Your physical exam will likely include a lung function test and a chest X-ray. They will also look for wheezing, which is a sign of blocked airways. This may include an inhaler, medication or both.
Blood Tests
Several types of tests can help your doctor determine whether you have asthma and, if so, how severe it is. Some measure how well your lungs work, while others look for certain allergy-causing substances. Your doctor may also use a combination of these test to confirm a diagnosis and to monitor how your treatment is working.
The most important diagnostic tool is a physical examination of your chest. Your doctor will listen to your breathing and ask you questions about when your symptoms happen (like during the night or at exercise) and what makes them better or worse. You might also want to keep a diary of your symptoms so that you can provide your doctor with information about when they occur and what seems to make them better or worse.
Your doctor might do blood tests to look for a certain type of white blood cell that is often present in people with eosinophilic asthma, a type of asthma that causes inflammation of the lungs. These tests, which aren’t widely available, include a sputum eosinophil count and provocative testing for exercise and cold-induced asthma.
