Population Stratification Analysis in Genome-Wide Association Studies

Differences in genetic background within two or more populations are an important cause of disturbance in case control association studies. In fact, when mixing together populations of different ethnic groups, different allele frequencies between case and control samples could be due to the ancestry rather than a real association with the disease under study. This can easily lead to a large amount of false positive and negative results in association study analysis. Moreover, the growing need to put together several data sets coming from different studies in order to increase the statistical power of the analysis makes this problem particularly important in recent statistical genetics research. To overcome these problems, different correction strategies have been proposed, but currently there is no consensus about a common powerful strategy to adjust for population stratification. In this chapter, we discuss the state-of-the-art of strategies used for correcting the statistics for genome-wide association analysis by taking into account the ancestral structure of the population. After a short review of the most important methods and tools available, we will show the results obtained in two real data sets and discuss them in terms of advantages and disadvantages of each algorithm.