The following are some testing and diagnostic procedures that are used by doctors and medical providers to identify asthma cases.

Spirometry

The Spirometry test is used to diagnose asthma and identify its severity.  In a spirometry test, you breathe forcefully into a tube and a device measures the amount of airflow passing through it.  This is known as forced expiratory volume (FEV). It also measures your total lung capacity i.e. the largest amount of air you are able to breath out. This is known as Forced Vital Capacity (FVC).

People will asthma will have restricted airflow, which will be represented by a decreased FEV and FEV:FVC ratio. If a patient is given medication to help open the lungs (bronchodilator) and then repeats the spirometry test, these numbers will show an improvement in most cases.

Peak Flow

A peak flow meter can be used to monitor breathing capacity and to check the effectiveness of asthma treatments. This is a handheld device that you breathe into as hard as you can. As you blow an arrow will rise, indicating how much air you were able to breathe. The higher the number, the better. Most devices will also be color coded. Green indicates a good number with adequate asthma control, yellow indicates a need to seek medical help, and red indicates an emergency.

Allergy Testing

Allergy testing is conducted if allergic asthma is suspected. Those suffering from allergic asthma will exhibit a worsening of symptoms after being exposed to the allergen. Immunoglobulin E (IgE)  is the substance your immune system releases after being exposed the substance you are allergic to. IgE causes inflammation, bronchoconstriction, and increased mucous production.

Skin test: Small pinpricks are made on the skin with a stick containing an allergen. If you are allergic to the substance, a big red welt will form around the area of the pinprick.

Blood test: IgE antibody levels will be elevated in the substance you are allergic to. For example, if you are allergic to pollen, the blood work will show high IgE in response to pollen.

Immune Panel

A patient will exhibit an increase in White Blood Cells (WBC) as well as increased eosinophils. The latter is associated with inflammation.

Imaging

Chest X-rays will reveal hyperinflation of the lungs in most cases. Imaging can also used to rule out other conditions.