Although a whole bunch of signs and symptoms can suggest developing or existing asthma, only a few of them are really specific to this condition. Therefore, doctors use different strategies that combine multiple diagnostic methods to properly diagnose asthma as early as possible.
When should a diagnosis of asthma be considered?
Shortness of breath, cough, and a "feeling of pain or tightness in the chest" are the most common symptoms of asthma. Since it is in most cases triggered by the presence of allergens, hypersensitivity to some of the most common allergens is also an important sign. Besides that, if the breathing difficulties are more intense after exercise, the patient should be thoroughly evaluated for asthma. These signs hold true both for children and adults.
Screening for asthma: How is it done?
There is no unified, strictly defined screening process for asthma. That is simply because many diseases related to the airways and lungs can produce similar symptoms. However, certain questionnaires can help in an initial evaluation of asthma. One of the questionnaires, which was developed for the purpose of research, consists of six questions regarding the most frequent scenarios in which people with asthma experienced worsened symptoms. The results were somewhat helpful, but questionnaires cannot confirm or rule out a diagnosis of asthma without a doctor’s examination.
How is asthma diagnosed?
To properly diagnose asthma, doctors follow the basic principles of medical diagnostics, which include the following steps:
- Medical history plays an important role in the diagnosis of asthma. In this step, the doctor asks the patient (or a parent) about the occurrence and severity of the symptoms. The aim is to first establish the chief complaints, and after that, the conversation goes into detail about the frequency of the symptoms, their severity, triggers, risk factors, other medical conditions, and finally – a family history of asthma and other chronic diseases. Although asthma cannot be classified as a genetic disorder, children with a family history of asthma are at a higher risk than people with no family history of pulmonary disorders.
- Physical examination is primarily based on the auscultation of the lungs with the stethoscope. The doctor will listen for sounds coming from the airways, through the lungs and chest wall, which are commonly present in asthma. The most common findings are wheezes and bronchial breathing (basically louder sounds than normal), especially noticeable during expiration. The doctor may also inspect the skin to see if there are some signs of allergic reactions, such as urticaria (hives).
- Spirometry is a functional testing of the lungs. It is a method which evaluates lung capacities and volumes during different phases of the respiratory cycle. Typically, in asthma patients, there is a reversible decrease of some respiratory volumes, particularly FEV1 (forced expiratory volume during the first second of expiration). By using a bronchodilator, FEV1 should return to normal or close to normal values. This is called a bronchodilation test, and albuterol inhalation is usually used to open up the airways before performing a spirometry again.
- Bronchoprovocation test is sometimes used by giving the patient some of the substances known to trigger symptoms in most asthma patients. If this test results in the appearance of asthma symptoms and a lowering of expiratory volumes, that proves the hypersensitivity of the airways and probably asthma.
- Allergy testing is necessary in order to discover whether there is a hypersensitivity to some allergens, which may produce asthma symptoms. Usually, the skin prick test is performed for the initial assessment of allergic reactions to the most common environmental allergens.
Differential diagnosis of asthma
The differential diagnosis of asthma is very complex, as many pulmonary conditions present with the same symptoms. Here are some of the disorders with similar signs and symptoms that need to be ruled out:
- Allergic rhinitis and sinusitis can be very persistent and they can mirror some of the symptoms of asthma, such as breathing difficulties, due to obstruction of the upper airways. However, these people should have normal spirometry results, as opposed to asthma patients.
- A foreign body in the airways can be a common cause of confusion while making a diagnosis, especially in children. Large foreign bodies cause obstruction of the trachea and that is a medical emergency. Small ones, however, can get stuck in some smaller branch of the airways, induce inflammation, and mimic the symptoms of asthma. If suspected, an x-ray should be performed to try to identify the foreign body and changes in the affected part of the lungs. Careful auscultation will also show the lack of respiratory sounds in the affected region of the lungs.
- Gastroesophageal reflux disease (GERD) produces burning sensations in the upper abdomen and lower chest, similar to those in asthma. Additionally, the regurgitated gasses and content from the stomach can be inhaled, which causes bronchoconstriction and airway obstruction. It is important to consider the possibility of GERD in all patients with breathing difficulties, especially when it comes to adult-onset asthma. The causal relationship between these two disorders is still under investigation.
- Other causes such as congestive heart failure, COPD, cystic fibrosis, pulmonary embolism, panic attacks, etc. can also present with breathing difficulties.