Large consortia have emerged to correlate phenotypes with specific variants at certain genetic loci but the strategies and pitfalls associated with combining phenotype data from varying studies have not previously been described in detail. A key recent critique of GWAS reveals a principal concern with effect sizes [Goldstein, 2009] suggesting that meta-analyses of complex traits may be the avenue to successful gene discovery. Consortia-based studies that incorporate the approaches described here will be essential to achieving the power to support investigations of effect sizes demonstrated to be typical [Garcia-Closas and Lubin, 1999].
