Sometimes asthma is difficult to diagnose because its symptoms are similar to other respiratory illnesses and infections. As a result, many people aren't aware that they have asthma. Often, the only symptoms might be a cough at night or wheezing during exercise. These signs usually are not alarming and are often passed off as bronchitis. To diagnose asthma, a doctor will probably look at your medical history and give you a thorough physical examination followed by laboratory tests. One lab test your doctor might use includes spirometry (spy-ROM-uh-tree), where an instrument is used to measure the amount of air taken in and released from the lungs. A similar lab procedure to measure lung capacity is peak flow monitoring. Chest X-rays as well as blood and allergy tests may be required for diagnosis.