Chunk #16 — Polygenic Risk Scores: A Bridge Between Population Variation and Individual Differences — PRS Practicalities — STEP 1: Identify a well-powered discovery GWAS in which your sample is not included and obtain summary statistics from that analysis.
effect sizes. In Figure 1, we use the example of the current largest GWAS of Schizophrenia which includes 36,989 cases and 113,075 controls (Schizophrenia Working Group of the Psychiatric Genomics, 2014). While it is not necessary for the discovery GWAS to have identified replicable genomewide significant loci (i.e., association p-values < 5 × 10−8), the ability for a GWAS to identify such loci may be seen as evidence for statistical power and its potential utility for PRS analyses.
