The chromosome 7q region association with rheumatoid arthritis in females in a British population is not replicated in a North American case-control series.

OBJECTIVE The single-nucleotide polymorphism (SNP) rs11761231 on chromosome 7q has been reported to be sexually dimorphic marker for rheumatoid arthritis (RA) susceptibility in a British population. We sought to replicate this finding and to better characterize susceptibility alleles in the region in a North American population. METHODS DNA from 2 North American collections of RA patients and controls (1,605 cases and 2,640 controls) was genotyped for rs11761231 and 16 additional chromosome 7q tag SNPs using Sequenom iPlex assays. Association tests were performed for each collection and also separately, contrasting male cases with male controls and female cases with female controls. Principal components analysis (EigenStrat) was used to determine association with RA before and after adjusting for population stratification in the subset of the samples for which there were whole-genome SNP data (772 cases and 1,213 controls). RESULTS We failed to replicate an association of the 7q region with RA. Initially, rs11761231 showed evidence for association with RA in the North American Rheumatoid Arthritis Consortium (NARAC) collection (P=0.0073), and rs11765576 showed association with RA in both the NARAC (P=0.038) and RA replication (P = 0.0013) collections. These markers also exhibited sex differentiation. However, in the whole-genome subset, neither SNP showed significant association with RA after correction for population stratification. CONCLUSION While 2 SNPs on chromosome 7q appeared to be associated with RA in a North American cohort, the significance of this finding did not withstand correction for population substructure. Our results emphasize the need to carefully account for population structure to avoid false-positive disease associations.

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