Journal Review 2 1.
Distinguishing severe asthma phenotypes: Role of age
at onset and eosinophilic
infiltration
(J Allergy Clin Immunol 2004;113:101-108)
2. Interrupter resistance and wheezing phenotypes at
4 years of age (Am J Respir Crit
Care Med 2004;169:209-213)
It is clear that asthma is a syndrome rather
than a disease. This heterogeneity is clear not only
in overall severity but also in the response to treatment,
including the propensity to undergo accelerated loss
of pulmonary function and development of fixed airflow
obstruction. Defining the phenotype is a central issue
in identifying the genetic components of any complex
disease. This definition is essential to identify the
genes involved and the relationship between genetic
and environmental influences. It is time to analyze
the clinical presentation of patients with asthma -
to look for markers that might allow description of
asthma phenotypes that will be useful in predicting
response to treatment or long-term outcome. With the
development of more accurate markers predicting ongoing
disease, it will be possible to evaluate a whole range
of early interventions in the future, early treatment
and intervention may prevent irreversible damage of
airways. In the former article, Miranda et al suggested
that differentiating severe asthma by age at onset and
presence or absence of eosinophils identifies phenotypes
of asthma, which could benefit subsequent genetic and
therapeutic studies.
The results of the invasive studies suggest
that there may be significant differences in the disease
mechanisms involved in the different asthma phenotypes
identified during childhood. Spirometric lung function
measurement is difficult to perform in young children,
because active cooperation is a prerequisite to make
a successful measurement. Measurement of airway resistance
with the interrrupter technique dose not require active
cooperation of the child and can be used even in preschool
children. MicroRint enables airway resistance to be
measured with the same ease as peak flow but without
effort or technique from the patient. To improve the
prognosis of asthma, it is important to distinguish
those children who will develop asthma from children
with transient symptoms only and to start treatment
as early as possible. The authors of the latter article
observed that mean interrupter resistance values were
higher in children with persistent wheeze as compared
with children with never and early transient wheezing
phenotypes. These results suggest that this technique
has a highly discriminative capacity and can be used
to select the asthmatic patients who require early intervention.
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