Just because you have symptoms of asthma, such as wheezing, coughing, or difficulty breathing does not mean that you have asthma. Other health conditions have symptoms that may mimic asthma symptoms. Let’s look at some common "asthma mimics."
Health Conditions That Mimic Asthma Symptoms
Because other health conditions may appear to be asthma and mimic asthma symptoms, your doctor will do a thorough exam and run any necessary tests to be sure your symptoms are due to asthma.
Conditions that can mimic asthma include:
- Sinusitis: Also called a sinus infection; an inflammation or swelling of the sinuses. Sinusitis and asthma often coexist.
- Myocardial ischemia: A disease of heart function characterized by inadequate blood flow to the muscle tissue of the heart. The main symptom of a heart attack is pain, but shortness of breath is another possible symptom of heart disease.
- Gastroesophageal reflux disease (GERD): A disorder in which stomach contents and acid flow back into the esophagus, causing frequent heartburn. Heartburn can cause asthma symptoms.
- Chronic obstructive pulmonary disease (COPD): A general term for several lung diseases, most commonly emphysema and chronic bronchitis, most commonly caused by cigarette smoking.
- Congestive heart failure: A heart condition in which the heart does not pump correctly, leading to a buildup of fluid in the lungs. This can cause exercise intolerance and shortness of breath.
- Bronchiectasis: Lung disease characterized by injury to the walls of the airways in the lungs; main cause is repeated infection.
- Upper airflow obstruction: A condition in which the flow of air is blocked by something, including enlarged thyroid glands or tumors.
- Vocal cord dysfunction: A condition in which the larynx (voice box) muscles close rapidly, causing difficulties in breathing.
- Vocal cord paralysis: Loss of function of vocal cords.
- Bronchogenic carcinoma: Lung cancer.
- Aspiration: Accidentally breathing food or other matter into the lungs.
- Pulmonary aspergillosis: Fungal infection of lung tissues.
- Respiratory syncytial virus (RSV): This virus can cause wheezing and pneumonia in babies and young children and may lead to childhood asthma.
How Are These Conditions Ruled Out and Asthma Correctly Diagnosed?
To make an asthma diagnosis and make sure your symptoms are not caused by another condition, your doctor will review your medical history, family history, and symptoms. They will be interested in any history of breathing problems you might have had, as well as a family history of asthma or other lung conditions, allergies, or a skin disease called eczema, which is related to allergies. It is important that you describe your symptoms in detail (coughing, wheezing, shortness of breath, chest tightness), including when and how often they occur.
You will be asked if you smoke now or have ever smoked. Smoking with asthma is a serious problem. Smoking is also a major factor in certain asthma mimics, including COPD and cancer. You will also be asked about past exposure to harmful chemicals, possibly at a job.
Your doctor will also perform a physical examination and listen to your heart and lungs.
There are many tests your doctor might perform, including lung function tests, allergy tests, blood tests, and chest and sinus X-rays. All of these tests can help your doctor determine if you have asthma and if there are other conditions affecting it.
For more information, see WebMD's article on Asthma Tests.
What Are Lung Function Tests?
Lung function tests (pulmonary function tests or PFTs) include several simple breathing tests to diagnose lung problems. The two most common are spirometry and methacholine challenge tests. These two tests, along with a history and physical exam, are the standards for making the diagnosis of asthma.
- Spirometry. This is a simple breathing test that measures how much and how fast you can blow air out of your lungs. Airway obstruction due to asthma or COPD is quickly revealed. Spirometry can be done before and after you inhale the asthma drug albuterol, a bronchodilator. Albuterol delivered in an asthma inhaler helps open blocked airways. If the airway obstruction improves after albuterol, that indicates you have asthma or COPD. Your doctor can use other tests and your medical history to help determine which one you may have. This test might also be done at future doctor visits to monitor your progress and help your doctor determine if and how to adjust your treatment plan.
- Flow volume loops. Simple spirometry tests only require that you exhale (blow out) forcefully, but flow-volume loops add rapid and maximal inhalation breathing maneuvers. Obstruction of air in the neck such as vocal cord paralysis or dysfunction are detected by this test. This upper airway narrowing can be confirmed using a CT scan of the neck or a flexible scope.
- Methacholine challenge test (MCT). Even if lung function tests are normal, you can still have mild, intermittent asthma. Your doctor may order a methacholine challenge test. During this test, you inhale increasing amounts of a mist of methacholine before and after spirometry. If lung function drops by 20% or more after a low dose of methacholine, that indicates you have asthma. This small decrease does not cause a worrisome asthma attack, and the effects of the methacholine are always successfully treated with albuterol.
- Diffusing capacity (DLCO). This simple test includes a 10-second breath hold to determine how well the lungs take up oxygen from the lungs. The DLCO is normal in people with asthma and low in smokers who have COPD.
What Is a Chest X-ray?
By viewing your lungs on an X-ray, your doctor can see if you have another health condition that may be causing asthma-like symptoms. Asthma may cause a small increase in the size of your lungs (called hyperinflation), but a person with asthma will usually have a normal chest X-ray. Patients with COPD will also have hyperinflation, but emphysema causes holes in lung tissue, called blebs or bullae, which are evident on a chest X-ray. A chest X-ray can also make sure you don't have pneumonia or lung cancer, particularly in smokers.
Other Tests for Conditions That May Mimic Asthma
There are some medical conditions that often make asthma harder to treat and control, in addition to being asthma mimics. These include allergies and GERD. If you are diagnosed with asthma, your doctor might also test you for these conditions, or treat them for several weeks to see if your asthma symptoms also improve.
For more information on allergies, GERD, and other triggers, see Causes of Asthma.