Assessing the validity of asthma associations for eight candidate genes and age at diagnosis effects

BACKGROUND

Before the advent of genome-wide association studies (GWAS), ADAM33, ADRB2, CD14, MS4A2 (alias FCER1B), IL13, IL4, IL4R, and TNF constituted the most replicated non-HLA candidate genes with asthma and related traits. However, except for the IL13-IL4 region, none of these genes have been found in close proximity of genome-wide significant hits among GWAS for asthma or related traits. Here we aimed to assess the reproducibility of these asthma associations and to test if associations were more evident considering the effect of age at diagnosis.

METHODOLOGY/PRINCIPAL FINDINGS

We systematically evaluated 286 common single nucleotide polymorphisms (SNPs) of these 8 genes in a sample of 1,865 unrelated Spanish individuals (606 asthmatics and 1,259 controls). We found that variants at MS4A2, IL4R and ADAM33 genes demonstrated varying association effects with the age at diagnosis of asthma, with 10 SNPs showing study-wise significance after the multiple comparison adjustment. In addition, in silico replication with GWAS data supported the association of IL4R.

CONCLUSIONS/SIGNIFICANCE

Our results support the important role of MS4A2, IL4R and ADAM33 genes in asthma and/or atopy susceptibility. However, additional studies in larger samples sets are needed to firmly implicate these genes in asthma susceptibility, and also to identify the causal variation underlying the associations found.

Prevalence of sensitization to Blomia tropicalis among young adults in a temperate climate

BACKGROUND

There are no previous population-based studies assessing the prevalence of Blomia tropicalis (BT). This investigation analyzes the prevalence of sensitization to BT and its contribution to asthma and related diseases among young adults in the Canary Islands.

MATERIAL AND METHODS

From a random sample of 9506 adults, aged between 20 and 44, who had previously answered a short respiratory questionnaire, a further 20% random sample was drawn. All participants filled in an extensive questionnaire, and they underwent spirometry and bronchial hyperresponsiveness (BHR) test and skin testing to several allergens as well as the determination of total IgE and specific IgE.

RESULTS

The prevalence of positive skin tests to BT was 13.8% (95% confidence interval [CI] 10.6-17.9%) and that of BT-specific IgE 17.9% (95% CI 14.2-24.5%). Sensitization to BT (positive skin tests or positive specific IgE) was 20.9% (95% CI 16.9-25.5%). Most of the subjects sensitized to BT were also sensitized to Dermatophagoides pteronissimus; however, only 7% displayed monosensitization to BT. Among subjects who exhibited BHR, sensitization to BT reached 46.7% (95% CI 32.7-60.9%), among those with asthma 50% (95% CI 26.8-73.2%), in subjects with rhinitis 37.2% (95% CI 28.1-47.6%), and in those suffering from dermatitis 25.9% (95% CI 18.7-34.5%). A strong association of BT sensitization with BHR and asthma before and after 15 years was found.

CONCLUSION

The prevalence of sensitization to BT among young adults in the Canary Islands is high, and it displays a close relationship with allergic respiratory diseases and dermatitis.

High prevalence of asthma and atopy in the Canary Islands, Spain

OBJECTIVE

To evaluate the prevalence of and risk factors for asthma and related conditions in the Canaries, Spain.

METHODS

From a randomised sample of 9506 adults aged 20-44 years who answered a short questionnaire, a random sample corresponding to 20% of the original was taken. Subjects classified as symptomatic in the previous survey and who were not included in the random sample were also invited to participate. The subjects completed a respiratory questionnaire, and underwent spirometry, bronchial hyperresponsiveness (BHR) test, skin tests and immunoglobulin E (IgE) measurements.

RESULTS

The random sample included 593 subjects. The prevalence of skin sensitisation to mites was 30.3% (95%CI 26.7-34.2) and the prevalence of IgE to mites 30.5% (95%CI 26.2-35.2). A prevalence of 40.6% (95%CI 35.9-45.5) was found for atopy, 14.1% (95%CI 11.1-17.1) for BHR and 4.2% (95%CI, 2.5-5.9) for asthma. The risk factors most strongly associated with asthma were atopy (OR 4.89, 95%CI 3.07-7.78) and respiratory infection before the age of 5 years (OR 2.78, 95%CI 1.66-4.67).

CONCLUSION

This study shows a high prevalence of sensitisation to mites, atopy, BHR and asthma in the Canaries, similar to that observed in English-speaking countries. We suggest that these findings could partially result from climatic conditions.