Diagnosis

In young children, the diagnosis of asthma can be confirmed by a clinical response to an inhaled bronchodilator. [√] In children aged 7 years and over, use spirometry to confirm the diagnosis of asthma. [√]

In the majority of children, the diagnosis of asthma is based on a history of recurrent or persistent wheeze in the absence of any other apparent cause (Table 1).

• Wheeze due to asthma is often accompanied by cough, shortness of breath, or both.
• A history of associated eczema, urticaria or a history of asthma in a first degree relative supports the diagnosis.
• In infants and toddlers, the first episode of wheeze may be difficult to distinguish from respiratory tract infections (acute bronchiolitis in infants or viral bronchitis in toddlers).

Tests to confirm the diagnosis

In young children, the diagnosis of asthma is usually confirmed by a clinical response to an inhaled bronchodilator.

• Only children over 7 years old are likely to be able to perform spirometry or peak expiratory flow rate (PEF) measurement consistently and reliably, to enable an objective assessment of lung function and bronchodilator response.
• Tests of bronchial hyperresponsiveness are rarely used in children.
• Exercise testing can confirm exercise-induced asthma in children.
   
  

Alternative diagnoses that are commonly confused with asthma

In new patients with a previous diagnosis of asthma, confirm that childhood recurrent non-specific cough has not been wrongly interpreted as asthma.

Recurrent non-specific cough

The pathophysiology of recurrent cough in the absence of wheeze appears differ from that of classic asthma and should not be confused with asthma.¹ Recurrent non-specific cough is a very common symptom in children, particularly preschool-aged children. There is usually no associated atopy or family history of asthma. Usually the child develops a cough in association with an upper respiratory tract infection. Typically:

• cough is dry
• coughing occurs in short paroxysms
• coughing is worse in the early hours of the morning and during exercise
• the paroxysm of coughing may be followed by a vomit. In between paroxysms, the child is very well with no tachypnoea or wheeze
• episodes last for 2-4 weeks
• cough is non-responsive to therapy.

Recurrent non-specific cough usually resolves by age 6 or 7 years and leaves no residual pulmonary pathology.

When cough is due to asthma, it is usually accompanied by some wheeze and episodes of shortness of breath.

• Cough can be the predominant symptom of asthma, but it is extremely rare for cough to be the only symptom.²
• The concept of the "cough-variant asthma" syndrome was popularised in the mid-1980s and it has become an all-embracing label for the symptom of recurrent cough. This has resulted in overdiagnosis of asthma and inappropriate therapy.

Chronic suppurative lung disease

The symptoms of chronic suppurative lung disease (chronic bronchitis and bronchiectasis) can be mistaken for those of asthma. Typically, the child with chronic suppurative lung disease presents with a history of cough as the major symptom. The cough usually does not disturb the child's sleep but typically is most prominent as a moist cough on waking in the morning.

Exercise-induced respiratory symptoms

Exercise-induced symptoms are commonly reported in children with asthma.

• Many children with asthma who report exercise-induced dyspnoea fail to demonstrate airflow limitation on formal exercise testing.³
• Misinterpretation of dyspnoea as asthma potentially leads to overtreatment.
• Exercise-induced laryngeal dysfunction, characterised by inspiratory stridor or acute air hunger, has recently been described in children and adolescents who are competitive athletes.⁴ Unlike vocal cord dysfunction, symptoms of laryngeal dysfunction usually only occur during competitive exercise and are difficult to reproduce in the laboratory.

In young children, care is needed to exclude non-asthma causes of wheeze. [√] When cough is the predominant symptom of suspected asthma, careful assessment is needed to avoid making an incorrect diagnosis of asthma, or instigating inappropriate management. (IV) Exercise-induced dyspnoea is not always due to asthma, even in children with a confirmed diagnosis of asthma. (IV) Asthma management in children should be based on a careful assessment of the pattern of asthma. [√]

Content Created (Thursday, 16 November 2006)