Abstract
Background: There is debate in the dermatology literature whether flexural eczema in childhood is really an atopic disease. After a systematic literature review, Flohr et al. concluded that the prevalence of atopy among subjects with flexural eczema varies greatly between study populations and is on average higher in hospital than in community settings. The association between flexural eczema in childhood and atopy in a wide range of study centers was investigated in phase two of the ISAAC study. Detailed results have already been published in the Journal of Allergy and Clinical Immunology. Methods: ISAAC Phase Two is a multicenter cross-sectional study, and 27 centers from 18 countries worldwide contributed data to the presented analysis. The prevalence of symptoms of flexural eczema was determined by parental questionnaire in eight-to twelve-year-old children (approximately 1,000 per center). In addition, a skin examination for flexural eczema was carried out in 30,031 children and a skin prick test for atopy was performed, using six common allergens: Dermatophagoides pteronyssinus, Dermatophagoides farinae, cat, Alternaria tenuis, tree and grass pollen. Some centers tested additional allergens of local relevance. A skin prick test was rated as positive, if the reaction minus the negative control was ≥ 3 mm, and a child was defined as atopic, if it had at least one positive skin prick test. Results: The prevalence of flexural eczema from skin examination shows a high variability and ranges from 0.4% in Kintampo, Ghana, to 14.2% in Östersund, Sweden. The prevalence of atopic flexural eczema (flexural eczema in combination with a positive skin prick test) varies from 0% in Kintampo, Ghana, and Ramallah, West Bank, to 7.0% in Östersund, Sweden. Nonatopic flexural eczema was most common (6.9%) in Östersund, Sweden, and least common (0.4%) in Kintampo, Ghana, and Cartagena, Spain. The proportion of atopic children among children with eczema varies largely among centers and in many cases, the proportion of nonatopic children prevails over the proportion of atopic children. In general, the prevalence of flexural eczema and the proportion of atopic children are lower in nonaffluent countries. The crude odds ratio for the association between flexural eczema and atopy is 2.52 (confidence interval 2.17-2.93) for affluent countries and 1.22 (confidence interval 0.8-1.85) for nonaffluent countries. The prevalence of flexural eczema symptoms in the past year (questionnaire) is on average higher than the prevalence from the skin examination. Regarding the association with atopy, however, the results are similar. Conclusion: The association between flexural eczema and atopy varies across study centers. It is therefore unlikely that atopy is the main cause of flexural eczema. The prevalence of flexural eczema as well as the association with atopy were higher in affluent compared to nonaffluent countries. It is possible that there are two distinct phenotypes of eczema, an atopic and a nonatopic one, the prevalences of which vary across the world. However, a more likely explanation is that atopy and flexural eczema are linked with the same affluence-associated environmental factors. In this context, the influence of potential risk factors will be investigated in the near future. In addition, a methodological comparison to assess the validity of questionnaire-derived prevalence data versus skin examination is already under way.
| Translated title of the contribution | International variation in prevalence of flexural eczema and atopic sensitization. Results from phase two of the International Study of Asthma and Allergies in Childhood (ISAAC Phase Two) |
|---|---|
| Original language | German |
| Pages (from-to) | 79-81 |
| Number of pages | 3 |
| Journal | Allergo Journal |
| Volume | 17 |
| Issue number | 1 |
| Publication status | Published - Feb 2008 |
Keywords
- Atopic eczema
- Atopy
- Flexural eczema
- Skin prick test
