Diagnosis of asthma generally includes three stages:

• Analysis of medical history
• Physical examination
• Lung function and other tests

Medical History

To start with, the doctor will analyze the patient’s specific symptoms and general health, with an emphasis on past episodes of similar symptoms. Doctors usually ask about exposure to allergens linked to asthma and any other health issues. The answers to these questions will help the doctor decide if the symptoms are caused by asthma or some other condition.

Specific questions will be related to the following:

• The nature and frequency of symptoms such as wheezing, chest tightness and shortness of breath
• Chances of exposure to allergens in dust or chemical fumes
• Any other existing allergies
• Habits such as smoking
• Interaction with any pet birds or pigeons
• Family history of asthma or any allergies in blood relatives
• Medications or supplements taken
• Health issues other than asthma

Physical Examination

During physical examination, doctors examine the patient’s breathing pattern while looking for allergy- or asthma-related signs such as wheezing, swollen nasal passages, runny nose and allergic skin reactions such as eczema. One of the key symptoms of asthma is high-pitched whistling sounds while breathing out – called wheezing.

Doctors usually carry out a physical examination using the following steps:

• Check the nose, throat and upper airways of the patient
• Listen to patient’s breathing with the help of a stethoscope
• Examine the skin for allergic rashes, eczema or hives.

Lung Function Test

Doctors may also check if the patient’s lungs are working properly using a spirometer. After taking a deep breath, the patient breaths out into a tube connected to the spirometer. The device shows the quantity of air breathed out and the speed at which air was breathed out in a given time period.

The results indicate any inflammation of airways or tightened up muscles around the airways. The spirometer is also used to measure breathing patterns after inhalation of irritants such as methacholine, which can narrow down the airways. This is called the bronchoprovocation test and measures the sensitivity of airways.
 

The tests are repeated after medication to track any improvement. If the results show an improvement, and the patient has a history of asthma symptoms, the diagnosis will most likely be asthma.

Other Tests

Based on the patient’s symptoms and medical history, doctors may order other diagnostic tests to help confirm asthma.

Some of them are as follows:

• Allergy testing, usually a skin patch test to determine what kind of allergens trigger a reaction in the patient
• A chest X ray or an ECG (echocardiogram) to help determine if a foreign object may be the cause of the symptoms.
• Tests to check for other conditions such as vocal cord dysfunction, reflux disease, or sleep apnea, which cause symptoms similar to that of asthma

Asthma in Young Children

It is more difficult to diagnose asthma in young children. Most asthmatic children develop the first symptoms before they turn 5. In children, it’s hard to differentiate symptoms of asthma from that of other conditions. This is because children usually have narrow airways which grow as the child grows. Young children usually have wheezing as a result of a cold or respiratory infection. This may or may not be a symptom of asthma in the future.

However, a child with frequent wheezing associated with respiratory infections may have asthma if the child shows signs of allergies such as skin rashes, the child is sensitive to airborne allergens such as pollens or the child’s parents have asthma.

Since a lung function test will be difficult to perform in young children, doctors usually rely on the child's signs and symptoms, medical history and physical examination in order to make a diagnosis.

Some additional signs of asthma in children may include the following:

• Frequent coughing during outdoor activities
• Faster or louder breathing
• Clear mucus and runny nose due to hay fever
• Less physical activity

References

• https://www.nhlbi.nih.gov/health/health-topics/topics/asthma/diagnosis
• http://www.mayoclinic.org/diseases-conditions/asthma/in-depth/asthma/art-20045198
• http://www.asthma.ca/corp/services/pdf/Diagnosis.pdf