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inhaled anti-cholinergic agents and placebo (Chang, McKean et al.20O4) in children with
persistent non-specifi c cough.
1.4.4 Investigations
There are few investigations that are specific to asthma in adults and children. There are no
diagnostic chest x-ray findings; the film may be normal, or there may be hyperinflation,
interstitial infiltrates or atelectasis with mucus plugging (Arthur 2000; Kercsmar 2006).
Hyperinflation, the most common pattern associated with asthma, can also be seen in
bronchiolitis and cystic fibrosis (CF) (Arthur 2000). Similarly, studies have shown that chest
x-rays are not useful in determining the difference between bronchiolitis and pneumonia
(Khamapirad and Glezen 1987; Davies, Wang et al. 1996; Byrnes, Vogel et al. 2005). In a
survey of school age children referred to a respiratory clinic,30Vo had prior diagnoses of
pneumonia on chest xray appearances but presented with symptoms identical to those
subsequently associated with their asthma diagnoses (Castro-Rodriguez, Holberg et al. 1999;
Mahabee-Gittens, Bachman et al. 1999).
Both total IgE and skin prick testing to common allergens have been used as a method of
detecting atopy, which overlaps the asthma syndrome. IgE levels appear to have been
increasing over the last decades coinciding with the increase in asthma (Burrows, Martinez et
al. 1989; Burney, Malmberg et al. 1997). Higher levels of IgE have been associated with
increased atopy and an increased incidence of wheeze (Call, Smith et al. L992; Heymann,
Carper et al. 2O04). An association has been demonstrated between the level of IgE and
airway hyper-responsiveness as measured by bronchial challenges (Muranaka, Suzuki et al.
1974; Burney, Britton et al. 1987). In a long term infant follow up study, the mean total serum
IgE at nine months of age was significantly higher among those who became persistent
wheezers compared to those who did not wheeze. Within the group of eady wheezers, those
who were wheeze free by ages I I and 16 years had total IgE levels similar to those who never
wheezed (Martinez 2002). However, the findings are not always consistent. Total IgE levels
were found to be higher in some cohorts of children than others despite similar asthma
prevalence, and the total IgE was higher in countries where house dust mite was the dominant
source of allergen @latts-Mills and Heyman 2006). The ECHRS study involving 37 centres in
16 countries demonstrated variation in the prevalence of response to at least one specific IgE
which ranged from 60Vo in Albacete (Spain) to 45Vo in Christchurch (New 7*aland) and was
not always consistent with asthma prevalence. The study also showed significant variations
between countries for total IgE and for prevalence of any specific IgE. At all ages women had
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