How is asthma diagnosed?

Since asthma symptoms can closely resemble symptoms of other respiratory problems like emphysema and bronchitis, asthma often goes undiagnosed for long periods of time. Some people live with asthma for years, thinking they have a bad cough or chronic bronchitis. Doctors diagnose asthma with laboratory tests such as spirometry (which measures the air inhaled and exhaled from the lungs), peak flow monitoring (which measures how much air a person can expel from the lungs), chest x-rays, blood tests, and allergy skin tests.