Diagnosis & natural history

A definitive diagnosis of asthma can be difficult to obtain in young children (see Figure 2). It is often not possible to measure airway function in order to confirm the presence of variable airway obstruction.

Figure 2 - Diagnosis

Presenting Features

Wheeze
Dry cough
Breathlessness
Noisy Breathing

Detailed history and physical examination

Pattern of illness
Severity/control
Differential clues

Probably asthma

Investigate or questions to seek
Causal factors
Exacerbating factors
Complications
Comorbidity

Possibly (or comorbidity)

Differential diagnostic tests and/or trials of asthma therapy

Base the diagnosis of asthma in children on:

the presence of key features and careful consideration of alternative diagnoses (see table 2)
assessment of the response to trials of treatment, and ongoing assessment
repeated reassessment of the child, questioning the diagnosis if management is ineffective.

Record the criteria on which the diagnosis has been made.

Table 2: Clues to alternative diagnoses in wheezy children (features not commonly found in asthma)

Clinical clue	Possible diagnosis
Perinatal and family history
Symptoms present from birth or perinatal lung problem	Cystic fibrosis; chronic lung disease; ciliary dyskinesia; developmental anomaly
Family history of unusual chest disease	Cystic fibrosis; developmental anomaly; neuromuscular disorder
Severe upper respiratory tract disease	Defect of host defence
Symptoms and signs
Persistent wet cough	Cystic fibrosis; recurrent aspiration; host defence disorder
Excessive vomiting or posseting	Reflux (and/or aspiration)
Dysphagia	Swallowing problems (and/or aspiration)
Abnormal voice or cry	Laryngeal problem
Focal signs in the chest	Developmental disease; postviral syndrome; bronchiectasis, tuberculosis
Inspiratory stridor as well as wheeze	Central airway or laryngeal disorder
Failure to thrive	Cystic fibrosis; host defence defect; Gastro-oesophageal reflux
Investigations
Focal or persistent radiological changes	Developmental disorder; postinfective disorder; recurrent aspiration; inhaled foreign body; bronchiectasis; tuberculosis

Indications for referral for specialist opinion/further investigation

Diagnosis unclear or in doubt
Symptoms present from birth or perinatal lung problem
Excessive vomiting or posseting
Severe upper respiratory tract infection
Persistent wet cough
Family history of unusual chest disease
Failure to thrive
Unexpected clinical findings e.g. focal signs in the chest, abnormal voice or cry, dysphagia, inspiratory stridor
Failure to respond to conventional treatment (particularly inhaled corticosteroids above 400 mcg /day or frequent use of steroid tablets)
Parental anxiety or need for reassurance

Prognosis of childhood asthma

Therapeutic decisions, particularly the introduction of prophylactic treatments may be influenced not only by the presence of persistent symptoms but by current understanding of the pathophysiology and the natural history of the disease.

If the factors associated with resolution and persistence of asthma presenting in childhood were not taken into account and every child presenting with wheeze was treated prophylactically, half of all children would be treated.

The major identifiable risk factors contributing to both the expression and persistence of asthma are considered below.

2.3.1 FAMILY HISTORY OF ATOPY

A family history of atopy is the most important clearly defined risk factor for atopy in children. Asthma is linked to both parental and sibling atopy. The strongest association is with maternal atopy. A maternal history of asthma and/or rhinitis is a significant risk factor for late childhood onset asthma and recurrent wheezing throughout childhood. The association of persistence of symptoms with maternal asthma and rhinitis weakens during the transition to adulthood. Evidence level 1+

2.3.2 CO-EXISTENCE OF ATOPIC DISEASE

Markers of allergic disease at presentation, (including skin prick tests, eosinophil counts and peripheral blood markers), are related to severity of current asthma and persistence through childhood, but as yet have not been shown to be related to the outcome of respiratory symptoms and their severity in adulthood.

2.3.3 EFFECT OF SEX

Male sex is a risk factor for asthma in prepubertal children and female sex is a risk factor for persistence of asthma in the transition from childhood to adulthood. Male children with asthma are more likely to "grow out" of their asthma in the transition to adulthood.

2.3.4 BRONCHIOLITIS IN INFANCY

Viral associated wheeze in infancy is often followed by wheeze in early childhood. This association weakens with advancing age and by 35-40 years ventilatory function and bronchial reactivity is similar to those who had no symptoms as children.

2.3.5 PARENTAL SMOKING

Maternal smoking is associated with significantly higher prevalence of wheezing illness in early childhood. However, there is no identifiable association between parental smoking and respiratory symptoms in adult life. Reducing the prevalence of smoking in the adult population, and particularly in women of childbearing age, would significantly reduce the prevalence of wheezing in young children.

2.3.6 BIRTH WEIGHT AND PREMATURITY

Wheezing is more common in young children who were born prematurely. In adulthood there are no consistent relationships between asthma and birth weight.

2.3.7 AGE AT PRESENTATION

The natural history of wheeze is dependent on the age at first presentation. The earlier the onset of wheeze, the better the prognosis. Available data from child cohorts show a "break point" at two years with the majority of those presenting before this age becoming asymptomatic by mid childhood (6-11 years). It must be remembered that coexistent atopy (see section 2.3.2 ) is a risk factor for persistence independent of age of presentation.

2.3.8 SEVERITY AND FREQUENCY OF EPISODES

Increased frequency and severity of wheezing episodes in childhood are associated with recurrent wheeze into adulthood.

2.3.9 LUNG FUNCTION MEASUREMENTS

There is a relationship between the level of pulmonary function in childhood and in adulthood. Persistent reduction in baseline airway function and increased airway responsiveness is associated with continuation of symptoms into adulthood.