A Rheumatoid Arthritis (R A) Genome-Wide Association Study (GWAS) Is

A rheumatoid arthritis (R A) genome-wide association study (GWAS) is being conducted on a cohort of Portuguese patients, including 907 cases with RA and 1,524 controls without RA. To examine the relationship between RA and hundreds of thousands of loci, logistic regression is performed. These findings are then compared to data from a European GWAS cohort of 4,036 RA patients and 6,959 non-RA patients. Finally, the findings of the Portuguese and European studies are merged in a meta-analysis. Based on these findings, the researchers discover three additional loci related with RA using a significance level criterion of 5 - 10⁸:   Previous research has found 30 loci that accounted for 35% of RA disease heredity. Which of the following statements is correct regarding this study?

A) Combining the results of the European and Portuguese studies into a meta-analysis decreases the power
B) Logistic regression is used because there is a stepwise increase in the strength of association from Locus 1 to Locus 3
C) The association between Locus 1 and RA in the meta-analysis is not statistically significant because the odds ratio is <1
D) The threshold used for the p-value in the meta-analysis is 5 × 10^-8 because of the large number of loci studied
E) With this meta-analysis, the 33 identified loci account for most disease heritability in RA