To examine the LD patterns within the CHRNB2 gene, we investigated the block structure using Haploview (25) and the CEPH (Centre d'Etude du Polymorphisme Humain) from Utah (CEU) HapMap (version 23a) samples. Figure 1 presents the LD patterns for 24 SNPs spanning the CHRNB2 gene with HapMap genotype data. Of these, 22 SNPs have MAF >0.05 and two SNPs were forced in the selection process because of prior information (rs2072658 and rs2072661). Our 13 tagSNPs captured 20 of the 22 total common HapMap SNPs with SNPs rs9427092 and rs3766925 not tagged at an r2 of 0.8 or greater. The LD structure indicates two distinct block regions with significant and suggestive SNPs from the single SNP analyses located within the second block. Using the eight genotyped SNPs within this region, we estimated six common haplotypes explaining 98% of the total frequency in the sample (Table 4). A haplotype analysis using the haplotype carrying the most common alleles for all the SNPs as the referent indicates that there is a significant global LRT at EOT (P = 0.03) and at 6-month follow-up
