Figure 1. Associations of MHC and Non-MHC Loci with Antineutrophil Cytoplasmic Antibody (ANCA)–Associated Vasculitis.

Panel A shows quantile–quantile plots of the results of the association test for all single-nucleotide polymorphisms (SNPs) with data of sufficient quality from the discovery cohort (left) and replication cohort (right). Triangles at the upper right of each graph indicate SNPs with −log₁₀ P values exceeding 30. The red symbols indicate SNPs other than those mapping to the major histocompatibility complex (MHC) for the discovery cohort and the three MHC SNPs specifically chosen for investigation in the replication cohort. The interrupted line indicates the estimated dispersion factor, lambda, and is estimated according to the ratio of the observed trimmed mean (calculated from the leftmost, linear half of the graph) to its expected value under the chi-square assumption. The shaded area indicates the concentration band for the plot and is defined by 95% probability bounds for each order statistic. Panel B shows the −log₁₀ P values for each SNP plotted against its chromosomal location in the discovery cohort. The red points indicate in the discovery cohort SNPs with a P value of less than 1×10⁻⁵ and a minor allele frequency of greater than 5%.