Asthma can go away. But this happens more often when asthma starts in childhood than when it starts in adulthood. When asthma goes away, it sometimes means it wasn’t there in the first place.

Asthma can be surprisingly hard to diagnose. The 3 main symptoms are:

• Wheezing
• Coughing
• Shortness of breath

But not all people with asthma have all 3 symptoms. And a number of other diseases can cause the symptoms, such as:

• Chronic bronchitis
• Emphysema
• Heart failure
• Acid reflux

The best way to diagnose asthma is with lung-function tests, not by symptoms. An instrument, called a spirometer, measures how much air you can exhale and at what rate. You will then take a couple puffs of an inhaler and see if this improves your air flow. Narrowed airways that open up with an inhaler is the classic feature of asthma.

A peak-flow meter is a simpler instrument that you can use at home. It measures how fast you can exhale but not the total volume. A peak-flow test is a good first step. But to get a definite diagnosis of asthma, you usually need other kinds of tests.

If you start having breathing problems again — and you haven’t had lung function testing — ask your doctor about it.