Asthma can be surprisingly difficult to diagnose, especially in young children and babies. The symptoms of asthma vary widely from person to person, and they can also resemble the symptoms of the flu and other respiratory infections. A chronic cough could be caused by asthmaor by a lingering respiratory bug or some other ailment (such as gastroesophageal reflux disease, or GERD, in adults).
The upshot is that it may take some time before a doctor will say the words, “These symptoms are due to asthma.” When trying to determine whether a person has asthma, a doctor has to consider the nature and pattern of symptoms such as wheezing and coughing, as well as family history. (A childs chance of developing asthma is 50% to 80% dependent on genetics, according to some estimates.)
In older children and adults, doctors may perform various lung function tests, such as spirometry or bronchoscopy. Spirometry involves blowing into a tube to measure lung function, which is not a practical test for very young children. In bronchoscopy, a lighted scope is used to examine the lungs, but this test is done much less often than spirometry.