I'm trying to get my head round the correct GWAS terminology. I keep seeing the terms like "tag", "lead" and "index" SNP to be used almost interchangeably and I would like to get a clarification from someone inside the field.
My (limited) understanding is as follows: Tag SNP - the SNP included on the genotyping microarray. Once we have a compendium of SNPs for a given sample we can use reference haplotypes to impute the rest of the SNPs. Lead SNP = Index SNP - the SNP assigned the highest association significance after we've run association analysis for all the imputed SNP. The other SNPs in high LD with the lead SNP will form the associated locus.
Am I correct in my understanding? Any other / better terms I should be aware of?