n Armitage Trend test; P value of association,0.05 in the replication study; Pcombined – P values calculated combining results from both the GWAS discovery and validation phase using logistic regression. doi:10.1371/journal.pone.0019719.t003 the Bonferroni correction threshold for multiple testing. Another limitation is that we only selected 77 SNPs to attempt for replication. Through our findings in this study, we suggest that it is unlikely to have any genetic risk factors with effect sizes 
of OR.1.8 which would have been observed otherwise. However it would be interesting to use the data available to Torin-1 chemical information perform meta-analysis or replication in other population in future studies to evaluate the significance of our results. Interestingly, evaluation of SNPs in candidate genes/regions previously reported in GWAS studies for asthma related traits revealed a strong overlap between atopy, allergic rhinitis and asthma as the QQ plots showed a significant deviation from null. Taking a closer look 1446362 at the SNPs in Materials and Methods Ethics Statement This study has been performed with the approval of the Institutional Review Board of National University of Singapore and is also in compliance with the Helsinki declaration. DNA samples used in this study were collected from ethnic Chinese participants following standard protocols of informed consent. The consent May 2011 | Volume 6 | Issue 5 | e19719 GWAS on Atopy and Allergic Rhinitis in Singapore obtained was a ��written consent��collected using the Participant Information Sheet which had information about the study. Study subjects A total of 4461 study subjects were recruited from the Singapore Chinese ethnicity through multiple volunteer recruitments in Singapore. Study subjects were subsequently 8664169 classified as atopy cases, AR cases and non-atopic and non-rhinitis healthy controls according to their disease status as determined by ARIA document based questionnaires. Diagnosing procedure included interview of medical history using a standardized questionnaire and skin prick test using a panel consisted May 2011 | Volume 6 | Issue 5 | e19719 GWAS on Atopy and Allergic Rhinitis in Singapore of common allergens in Singapore such as Dermatophagoides pteronyssinus, Blomia tropicalis, Elaeis guineensis and Curvularia lunata. A wheal diameter of 3 mm or greater is considered as a positive SPT response. A positive control with histamine and a negative control of saline were always used. SPT was performed on the volunteers only if they have not taken any anti-allergic drugs especially antihistamines for at least 3 days prior to the test. Atopy is defined by a positive SPT reaction to either one of the dust mite allergens. AR is thus diagnosed based on the presence of atopic status and typical AR symptoms as defined by the ARIA guidelines i.e., two or more AR symptoms persisting for four or more days a week during the past year. Conversely, the subjects with NANR are confirmed with no atopy and no typical AR symptoms. Subjects who could not be recruited into any of the above categories were excluded from study. Genomic DNA was extracted from buccal cells obtained from a mouthwash of 0.9% saline solution following an in-house standardized protocol. In short, the buccal cells were pelleted and lysed; DNA was extracted using the phenol-chloroform phase-separation technique purified by two washes in ethanol, with the DNA pellet resuspended in reduced Tris-EDTA buffer. Samples were quantified in triplicate on the
