How is asthma diagnosed?

Asthma is mainly a clinical diagnosis based on a history of repeated acute attacks of wheezing, coughing and breathlessness, often with a positive family history of allergy.

Asthma is mainly a clinical diagnosis based on the past and family history.

The most useful special investigations are:

  1. Lung function tests: Children over the age of 5 years can use a peak flow meter to measure their peak expiratory flow rate. They take a deep breath and then blow as hard as they can into the peak flow meter, which measures how fast they can blow air out of their lungs (like blowing out a candle). Children with asthma have a lower peak flow rate than normal due to their narrow airways.
  2. Skin tests: Skin tests are done by placing a drop of a specific allergen on the child’s forearms. The underlying skin is then pricked with a special lancet through the drop of allergic testing solution. The test site is examined after 15 minutes. A swelling (wheal) at the test site indicates that the person is allergic to that allergen. Skin tests are simple to perform, cheap and accurate. A blood test (RAST) can also be used to identify a response to specific allergens. The child should not be on an antihistamine for 48 hours before performing a skin prick test. Skin tests are used as supportive evidence for asthma as they diagnose allergies only.
  3. Response to a short acting bronchodilator: A good clinical and peak flow rate response to a dose of inhaled bronchodilator is the best way to confirm the clinical diagnosis acute asthma. In preschool children the diagnosis usually depends on a clinical response to treatment while in older children an improvement in the peak flow is important.

Asthma presents with repeated episodes of wheezing, coughing or shortness of breath that respond to bronchodilators.

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