Detection and diagnosis

There is no ‘gold standard' for the diagnosis of asthma. Recommendations regarding the tools and techniques for asthma diagnosis are based on consensus opinion among respiratory physicians. The diagnosis of asthma is based on:

• history
• physical examination
• supportive diagnostic testing, including spirometry.

History

The presence of one or more of the following characteristic symptoms is suggestive of asthma:

• wheeze
• chest tightness
• shortness of breath
• cough.

Asthma is especially likely if any of the following applies:

• Symptoms are recurrent or seasonal
• Symptoms are worse at night or in the early morning
• Symptoms are obviously triggered by exercise, irritants, allergies or viral infections
• Symptoms are rapidly relieved by a short-acting bronchodilator (See Diagnostic testing).

However, the symptoms of asthma vary widely from person to person. The absence of typical symptoms does not exclude the diagnosis of asthma.

To detect possible asthma, ask about:

• current symptoms
• pattern of symptoms (e.g. course over day, week or year)
• precipitating or aggravating factors (e.g. exercise, viral infections, ingested substances, allergens)
• relieving factors
• impact on work and lifestyle
• home and work environment
• past history of eczema, hay fever, previous events
• family history of atopy.

In some Aboriginal and Torres Strait Islander communities, asthma is commonly known as ‘short wind'. Health professionals should be aware of this term so as to avoid potential misdiagnosis or confusion with other causes of exertional dyspnoea.

For more information about taking a thorough asthma history, including questions to ask regularly at ongoing review, see Ongoing care.

Examination

Examine the chest for hyperinflation and wheeze. Also look for signs of allergic rhinitis, which commonly co-occurs with asthma, because its presence will affect management (See Asthma and allergy). Note that: 

• wheeze is suggestive, but not diagnostic of asthma
• the absence of physical signs does not exclude a diagnosis of asthma.
• crackles on chest auscultation indicate an alternate or concurrent diagnosis.

Expiratory wheeze suggests asthma but is not pathognomonic. [√] The absence of physical signs does not exclude a diagnosis of asthma. [√] Look for signs of allergic rhinitis in patients with suspected asthma. [√] Do not rely on peak flow meters for assessing airflow limitation in the diagnosis of asthma. [√]

Content Created (Thursday, 16 November 2006)