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.