The SNP minor allele frequency (MAF) for the control population in the IFIH1 gene was reported to be 40.4% in the initial round, and 38.7% in the follow-up round (Smyth et al., 2006); that in the type 1 diabetes population was 35.3% in the first round, and 34.0% in the second round, each with thousands of samples. The control MAF in Table 5 is 40.8%, consistent with the value in (Smyth et al., 2006). However, the MAF for the rheumatoid arthritis samples in Table 5 is 36.2%, larger than the MAF for the type 1 diabetes samples. The weaker association signal in rheumatoid arthritis study as compared to diabetes study implies a larger sample size requirement for its detection, and as a result, ESS method proves to be important in incorporating extra sibling samples to increase the sample size.
