Asthma is a chronic inflammatory disease of the airways, associated with widespread, variable outflow obstruction. Clinically, this manifests as:
- Difficulty breathing
- Chest tightness
The outflow obstruction reverses either spontaneously or with medication. The underlying inflammation is associated with bronchial hyperresponsiveness (BHR) or airway hyperreactivity to a variety of stimuli (eg environmental allergens and irritants).
Diagnosis of asthma in children is difficult because of the complex nature of the disorder in the young. Accurate diagnosis in primary care remains an important challenge - recent guidelines (British Thoracic Society 2008) recommend recording the basis on which the diagnosis is suspected and managing or investigating children further according to the probability of asthma.
Many people consider 'wheeze' synonymous with asthma, yet there are many different causes of wheeze in childhood and increasingly we recognise different 'phenotypes' of wheezing. These are usually determined retrospectively as they depend on the pattern of symptoms over time:
- Episodes of wheezing, cough and difficulty breathing associated with viral upper respiratory tract infections (URTIs) with no persisting symptoms. Common in infants and preschool children (about 30% of children aged under 3) but most will have stopped having recurrent symptoms by school entry.
- Some children who wheezed early, will go on to develop wheezing with other triggers so that they develop interval symptoms, similar to older children with classical atopic asthma.
- Atopic asthma is more common in school-aged children; symptoms occur often with identifiable triggers and often alongside eczema or hay fever but, even in this age group, non-atopic asthma is as frequent as the atopic variant.
The diagnosis of asthma is clinically based without a single confirmatory diagnostic test, only corroboration of the diagnosis with changes in lung function or response to treatment. In the past, lung function testing was not possible before the age of about 5 years, but several newer tests may enable testing somewhat earlier (eg specific airways resistance, impulse oscillometry and measurements of residual volume) although none as yet has been fully evaluated.
- The UK has one of the highest prevalences for childhood asthma internationally, with about 15% children affected.
- The prevalence is 8-10 times higher in developed countries than in developing countries.
- The prevalence of 'any wheeze' over recent months (usually taken as within the last year) amongst children has risen from about 10% in the 1960s to 20-30% in the 1990s. There is some evidence of of a possible flattening of this rise from the late 1990s onwards. An increasing percentage of currently wheezing children also have a diagnosis of asthma.
- Interestingly, there has been a recent decline in the prevalence of moderate-to-severe asthma in 13-14 year-olds in the UK. This can be explained in part by the delivery of more effective treatment (inhaled corticosteroids primarily) but does not explain the concurrent decline in mild asthma in the same age range.
- Children still die from asthma (27 recorded deaths from asthma in 2005) and there is still a significant morbidity associated with the disease, particularly severe childhood asthma, despite therapeutic advances.
- Prevalence is higher in lower socioeconomic groups in urban areas.
- There are gender differences. Boys are affected more before puberty (3 times greater prevalence). Prevalence is equal in adolescence, but adult-onset asthma is more common in women.
- The increasing prevalence of asthma is mirrored by the increasing prevalence of childhood obesity. Prospective studies suggest that obesity increases the risk of subsequent asthma, although the underlying mechanisms are unclear, but obesity also increases the clinical severity of asthma and reduces quality of life for children with asthma.
There is a long list of possible risk factors:
- Personal history of atopy.
- Family history of asthma or atopy.
- Triggers (eg allergens such as pollens, animal dander), dust, exercise, viruses, chemicals, weather changes, emotional factors, irritants and smoke.
- Urban environment.
- Socioeconomic stresses.
- Prematurity and low birthweight.
- Viral infections in early childhood.
- Maternal smoking.
- Early exposure to broad spectrum antibiotics.
- Age at presentation - those presenting aged younger than 2 years tend to have become asymptomatic by mid-childhood.
- Coexisting atopy is a risk factor for persistence of asthma.
- Family history of atopy, particularly maternal atopy.
- Sex - male sex is a risk factor for asthma in prepubertal children whilst female sex is a risk factor for persistence of asthma into adulthood. Girls are less likely to 'grow out' of their asthma.
- More severe and frequent wheezing episodes are associated with asthma persisting into adolescence.
- Abnormal lung function, both baseline airway function and increased airways responsiveness.
When taking a history:
- Ask about typical symptoms:
- Wheeze - very common, high-pitched, polyphonic and present in expiration. As severity increases, it may be present during expiration and inspiration. In the most severe episode, it may be completely absent. It must be distinguished from the inspiratory, monophonic noise of stridor which is associated with reduced or impaired upper airway patency. Note that parental understanding of wheeze may include whistling, squeaking or gasping sounds, or a different style, rate or timbre of breathing. Clarify what a patient or their parent mean by wheeze.
- Cough may be the only symptom in children (particularly with exercise-induced asthma and nocturnal asthma). The cough is usually dry and nonparoxysmal. The nocturnal cough of asthma usually occurs after midnight. About 10% of preschool children have chronic cough without wheeze at some time. Chronic cough on its own is a poor marker for asthma and one should always consider other diagnoses. Children with cough-predominant asthma should show improvement on a short trial of asthma medication and return of symptoms on discontinuation of treatment.
- Chest tightness with or without other symptoms occurs, particularly with exercise and at night in asthma.
- Breathlessness varies according to severity. Is the child able to play, run or walk? The most severe attacks are accompanied by breathlessness at rest, paucity of speech, agitation, feeding difficulties and attenuated cry (in infants). Children become drowsy and confused and, in adolescents particularly, symptoms develop late as severity increases.
- Identify triggers - eg viral URTIs, cold air, dust, pets, pollen, change in weather, exercise.
- Ask about symptoms in the intervals between exacerbations.
- What has been the pattern over time? What is the current frequency of acute episodes?
- Ask about atopic illnesses in the patient and their family.
- Check previous diagnoses, treatment and concordance with treatment.
- Check for previous emergency contacts with healthcare professionals with related symptoms.
- What is the impact on the child's life? How much school has been missed?
Signs will vary according to the severity of asthma and the severity of any exacerbation.
During episodes, check for:
- Widespread wheeze.
- Increased work of breathing.
- Pulse rate.
- Respiratory rate.
- Oxygen saturation.
- Peak expiratory flow rate (PEFR) (in children aged over 5).
- Response to bronchodilator therapy.
Between episodes, there may be no clinical signs but check for:
- Hyperexpansion and Harrison's sulci.
- Clues to other possible diagnoses.
|Clues to alternative diagnoses in the wheezy child|
|Wheeze present from birth:
|Wheeze present shortly after birth:
|Sudden onset in a previously well child:
After the initial clinical assessment, it is usually possible to determine the relative likelihood of asthma in a particular child and the need for further investigations (although tests may only be needed if there is doubt about the diagnosis or significant disability from the disorder):
- High probability of asthma - move directly to a trial of treatment, the choice of which will be based on assessment of current asthma severity. Reassess in 2-3 months. Investigate further those who show a poor response to treatment or who have severe disease.
- Low probability of asthma - consider more detailed investigations and referral, particularly where an alternative diagnosis seems likely.
- Intermediate probability of asthma - in some and especially those aged under 4-5 years, there may be insufficient evidence to make a firm diagnosis. Approaches in this instance include:
- Watchful waiting with review.
- Trial of treatment with review - where beneficial, treat as asthma.
- Spirometry and reversibility testing.
|Features increasing the probability of asthma:||Features decreasing the probability of asthma:|
With older children with an intermediate probability of asthma, diagnostic tests such as peak expiratory flow rate (PEFR) and forced expiratory volume in one second (FEV1) can provide objective measures of airways obstruction but these may be normal between episodes of bronchospasm and provide poor discrimination with other conditions that also cause airways obstruction. Spirometry is usually possible from about 5 years old, although there is wide variation, and is dependent on the child's co-operation and comprehension of the task.
Where there is evidence of airways obstruction, looking for changes in PEFR or FEV1 10 minutes after the use of a bronchodilator (reversibility usually taken as >12% subsequent improvement in lung function). Also, look for response to a treatment trial over a defined time period, as this adds further weight to the diagnosis of asthma.
Where no evidence of airways obstruction is found with spirometry consider referral and testing for:
- Atopic status (skin tests*, blood eosinophilia or raised specific immunoglobulin E (IgE) to a cat, dog or mite).
- Bronchodilator reversibility.
- Bronchial hyperresponsiveness (with methacholine, exercise or mannitol)* - high negative predictive value (86-100%) but less useful as a positive predictive tool (55%).
(*These tests are not normally available within primary care.)
Chest X-rays should not be used as part of the initial work-up in primary care of children aged 0-6 years in the absence of a specific clinical indication.
Indications for referral
- Diagnosis unclear or in doubt.
- Symptoms present from birth or a perinatal lung problem.
- Excessive vomiting/possetting.
- Severe URTI.
- Persistent wet cough.
- Family history of unusual chest disease.
- Nasal polyps.
- Unexpected clinical findings (eg focal chest signs, abnormal cry or voice, dysphagia, stridor).
- Failure to respond to conventional treatment (especially corticosteroids above 400 micrograms/day). Vocal cod dysfuncrtion can mimic steroid refractory asthma.
- Frequent use of oral steroids.
- Parental concerns or anxiety.
Further reading & references
- Asthma, Prodigy (2007)
- British Guideline on the Management of Asthma; British Thoracic Society (BTS) and Scottish Intercollegiate Guidelines Network - SIGN, 2008 (latest revision May 2011)
- Piippo-Savolainen E, Korppi M; Wheezy babies--wheezy adults? Review on long-term outcome until adulthood after early childhood wheezing. Acta Paediatr. 2008 Jan;97(1):5-11. Epub 2007 Dec 3.
- Anderson HR, Gupta R, Strachan DP, et al; 50 years of asthma: UK trends from 1955 to 2004. Thorax. 2007 Jan;62(1):85-90.
- Townshend J, Hails S, McKean M; Diagnosis of asthma in children. BMJ. 2007 Jul 28;335(7612):198-202.
- The Asthma Divide, Asthma UK
- Chinn S, Downs SH, Anto JM, et al; Incidence of asthma and net change in symptoms in relation to changes in obesity. Eur Respir J. 2006 Jul 26.
- Story RE; Asthma and obesity in children. Curr Opin Pediatr. 2007 Dec;19(6):680-4.
- Cates C; Chronic asthma. BMJ. 2001 Oct 27;323(7319):976-9.
- Halken S; Prevention of allergic disease in childhood: clinical and epidemiological aspects of primary and secondary allergy prevention.; Pediatr Allergy Immunol. 2004 Jun;15 Suppl 16:4-5, 9-32.
- Warman KL, Silver EJ, Stein RE; Asthma symptoms, morbidity, and antiinflammatory use in inner-city children.; Pediatrics. 2001 Aug;108(2):277-82.
- Chen E, Bloomberg GR, Fisher EB Jr, et al; Predictors of repeat hospitalizations in children with asthma: the role of psychosocial and socioenvironmental factors.; Health Psychol. 2003 Jan;22(1):12-8.
- Frank P, Morris J, Hazell M, et al; Smoking, respiratory symptoms and likely asthma in young people: evidence from postal questionnaire surveys in the Wythenshawe Community Asthma Project (WYCAP). BMC Pulm Med. 2006 May 22;6:10.
- Thomas M, Custovic A, Woodcock A, et al; Atopic wheezing and early life antibiotic exposure: a nested case-control study. Pediatr Allergy Immunol. 2006 May;17(3):184-8.
- Akobeng AK, Heller RF; Assessing the population impact of low rates of breast- feeding on asthma, coeliac disease and obesity: the use of a new statistical method. Arch Dis Child. 2006 Jul 13.
- Weinberger M, Abu-Hasan M; Pseudo-asthma: when cough, wheezing, and dyspnea are not asthma. Pediatrics. 2007 Oct;120(4):855-64.
- Definition, assessment and treatment of wheezing disorders in preschool children: an evidence-based approach; European Respiratory Society (2008)
|Original Author: Dr Richard Draper, Dr Chloe Borton||Current Version: Dr Gurvinder Rull|
|Last Checked: 17/09/2010||Document ID: 1103 Version: 22||© EMIS|
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