A need for phenotyping pediatric asthma in epidemiologic studies

Epidemiological studies on pediatric asthma reveal a substantial variation in the prevalence of the disease. Differing population-specific data on the occurrence of the disease, defined as a physician-diagnosed asthma, are attributed to differences in risk factors, nosologic preferences, availability of diagnostic facilities, socio-economic factors, etc. As a result some findings could be affected by so-called underdiagnosis although in some populations overdiagnosis of pediatric asthma cannot be excluded. Diagnosing pediatric asthma can be difficult even in clinical setting. Among factors hampering that process heterogeneity of the disease plays an important role. Evidence show that asthma is not a single disease but it is a complex syndrome composed of similarly manifested disorders. As a result a significant scientific effort is directed to describe phenotypes of pediatric asthma. Two well known approaches to phenotyping include clinical and etiological assessment. The former approach takes into account the clinical presentation. The latter one involves recognition of the circumstances that precede the symptom manifestation in the disease: 'virus-induced asthma', 'exercise-induced asthma', 'allergen-induced asthma', 'unresolved asthma'. The mentioned approaches do not provide means of complete classification of the disease. A relatively novel and promising research area in the field of phenotyping asthma takes advantage of biomonitoring. Biomarkers of allergy and immunological responses are used in clinical setting (for example: assessment of atopy, eosinophils count, FENO), however many tests need more validation. Of particular interest is availability of non-invasive biomarkers, their repeatability, sensitivity and specificity. Several national and international guidelines and recommendations point to the importance of specific studies addressing the role of biomonitoring in phenotyping asthma. Еpidemiological perspective investigations into biomarkers in pediatric asthma can contribute to observational and analytical goals. Focus on specific phenotypes and its components could provide a better opportunity to explore asthmatic disorders in children. Epidemiological projects should also address validation issues. Both research directions deserve more attention in epidemiological studies on pediatric asthma.