The diagnosis of asthma is dependent on the overall risk factors of the child and a careful consideration of alternative diagnoses. Definitive diagnosis of asthma is dependent on a history of reversible airway obstruction that responds to bronchodilators, in addition to symptom improvement with inhaled bronchodilators or corticosteroids. Generally, children with a high probability of asthma, based on history, examination, and risk factors, may be treated empirically. Children with an intermediate or low probability of asthma generally require further testing, as do children with a high probability but a poor response to treatment. Some guidelines recommend confirmation of the diagnosis with tests in all children old enough to take the tests (e.g., children 6 years and above).
Absolute markers of asthma risk do not exist. The combination of risk factors, in children with frequent wheezing episodes before the age of 3 years, has been used to construct a predictive index of persistent asthma risk that has been subsequently modified. The main value of this index appears to be in its high negative predictive value, although this is increasingly challenged, with some authors noting that a negative modified asthma predictive index may not signify a decrease in future risk of asthma.
Recurrent symptoms of wheezing, dry cough especially at night or in early morning, and shortness of breath in response to recognised triggers such as change in temperature, viral infections, exercise, and emotion are characteristic of asthma. Parents may label various respiratory noises incorrectly as wheezing, and parental perception should be evaluated. The diagnosis is supported by other features of atopic disease, such as eczema, atopic dermatitis, and allergic rhinitis in the child or first-degree family members.
International guidelines from the Global Initiative for Asthma (GINA) recommend a probability-based approach plus a trial of treatment for children 5 years and younger, as most children in this age group cannot perform lung function tests reliably. However, in children 6 years and above, GINA recommends confirmation of the asthma diagnosis with a test of variable expiratory airflow limitation (see Diagnostic criteria section).
The initial assessment of children suspected of having asthma is focused on the presence of key features in the history and clinical examination as well as on careful consideration of alternative diagnoses. The basis on which the diagnosis of asthma is suspected should be recorded. Using a structured questionnaire may produce a more standardised approach to the recording of presenting clinical features and the basis for a diagnosis of asthma.
1. In children with a high probability of asthma (based on features in their history, examination, and medical records):
Move straight to a trial of treatment and reserve further testing for those with a poor response.
2. In children with a low probability of asthma:
Consider more detailed investigation, particularly for other diagnoses, and specialist referral.
3. In children with an intermediate probability of asthma who can perform spirometry and have evidence of airway obstruction, offer a reversibility test and/or a trial of treatment for a specified period:
If there is reversibility, or if treatment is beneficial, treat as asthma.
If there is insignificant reversibility, and/or treatment trial is not beneficial, consider tests for alternative conditions.
4. In children with an intermediate probability of asthma who can perform spirometry and have no evidence of airway obstruction, consider testing for atopic status, bronchodilator reversibility, and, if possible, bronchial hyper-responsiveness using methacholine or exercise.
5. In children with an intermediate probability of asthma who cannot perform spirometry, consider testing for atopic status and offering a trial of treatment for a specified period:
If treatment is beneficial, treat as asthma.
If treatment is not beneficial, stop asthma treatment, and consider tests for alternative conditions and specialist referral.
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