Finally, when there are several putative association signals in a region of high LD, dense genotyping in replication studies may help elucidate whether they represent independent loci, each with its own effect in the trait, or whether one or all are “passenger” markers, which have no effect conditional on the true underlying causal variant. Detailed discussion of fine mapping issues is beyond the scope of this review, but in light of the effort involved, such “fine mapping” efforts should arguably be reserved for loci with credible evidence for association, e.g. loci with markers that have been replicated exactly, as discussed in the next section. [33]
