The LD map and each SNP-associated P-value are depicted in Figure 1. Rs1044394 and rs6010918 are in strong LD in both AAs and EAs (r2 = 0.91 and 0.81 for AAs and EAs, respectively), which explained the evidence for association of both SNPs with ND (FTND) in the combined sample and in each population group (Table 3). To exclude the possibility that multiple observed effects were caused by LD with a single true risk allele, we performed conditional haplotype analysis on the combined sample with race, age and sex as covariates. As expected, both SNPs showed a significant global association with ND (P = 0.0046). The global association disappeared when conditioned on rs1044394 (P = 0.24), but remained significant when conditioned on rs6010918 (P = 0.047). This analysis suggests that the significant association of rs6010918 with ND arises from its high correlation with rs1044394. When a similar analysis was used for the FTND binary trait, the effects of rs1044394 and rs6010918 could not be disentangled.
