Distinguishing phenotypes of cough and wheeze in young children
Published Online: September 25, 2013
Young children with wheeze and chronic cough vary greatly in their clinical presentation. Some children wheeze only when having a cold (often called viral wheezers), while others wheeze in the absence of colds, for instance during exercise or after contact with pollen or pets. The long term outcome of preschool wheeze is variable: some children wheeze only as toddlers and become asymptomatic when they get older; others develop asthma that persists into school age or even adulthood. There have been various attempts to classify children into phenotypes, i.e., groups of children with more homogenous patterns of disease that might reflect distinct underlying pathologies. In the past these attempts have been based on expert opinion, for instance classifying wheeze into ‘episodic viral’ and ‘multitrigger wheeze’ or into ‘transient early,’ ‘persistent,’ and ‘late onset wheeze.’ More recently a number of studies have used more objective statistical methods (cluster analysis) to identify phenotypes from data collected through surveys on large numbers of children.
In their recent article in The Journal of Allergy & Clinical Immunology (JACI), Spycher et al investigate whether phenotypes identified by such an approach – in their case latent class analysis – are reproducible in independent samples of children. They analyzed data on symptoms of wheeze and cough collected at preschool age and again at early school age, and physiologic measurements of lung function, atopy, and bronchial responsiveness made at school age. In an earlier study using this approach, the authors had identified 3 phenotypes of wheeze and two phenotypes of cough which differed in prognostic outcomes 5 years later. In the present study they applied the same approach to a new sample of 903 children from the general population. The five-phenotype model again identified two phenotypes of cough and three phenotypes of wheeze. Two of the wheeze phenotypes were closely similar in clinical characteristics and prognosis to phenotypes found in the original study: atopic persistent wheeze (persistent multiple trigger wheeze and chronic cough, atopy, and reduced lung function with a poor prognosis) and transient viral wheeze (early-onset transient wheeze with viral triggers with a favorable prognosis).
The authors conclude that the phenotypes which were reproduced are likely to reflect distinct disease processes. However, not all phenotypes were consistently replicated, suggesting that differences in study design, particularly the age when measurements were taken, may have affected results. While the results provide support for the existence of different disease entities within the large group of children with asthma-like symptoms, they also suggest that findings from individual cluster analyses should be interpreted with caution and need validation in independent samples. Nevertheless, as evidence increases in support of different disease entities, the prospect of individualized treatment becomes closer to reality.
The Journal of Allergy and Clinical Immunology (JACI) is an official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.