Genome-wide association studies (GWAS) usually rely on the assumption that different samples aren’t from closely related individuals. If you’re using combined datasets that have been genotyped on different platforms, though, how do you detect duplicates and close relatives?
The dbGaP team at NCBI developed a new software tool and rapid statistical method called Genetic Relationship and Fingerprinting (GRAF) to do exactly that. At NCBI, we use GRAF as a quality assurance tool in dbGaP data processing. We’re presenting this tool publicly so any researcher can check the quality of their own data.
GRAF uses two statistical metrics to determine subject relationships directly from the observed genotypes, without estimating probabilities of identity by descent (IBD), or kinship coefficients, and compares the predicted relationships with those reported in the pedigree files. Please see the PLOS ONE article published in July 2017 for a detailed description of GRAF.
A recent update to GRAF adds the ability to determine subject ancestries. For more information on this addition, visit Poster #1322T, “Quickly determining subject ancestries in large datasets using genotypes of dbGaP fingerprint SNPs”, on Thursday, October 19th from 3-4 in the Exhibit Hall at ASHG.