anchor.diff:  "pooled" is used to denote studies of pooled DNA.
   
   For each identified SNP, we extract:
  +
   * Gene, as reported by the author
   * rsID, or other SNP identifier, and risk allele (as reported)
   * Risk allele frequency in controls (if not available among all controls, among the control group with the largest sample size)
  
positive.code: In cases where studies containing multiple GWAS analyses are not split, generally because <5 associations are identified for each analysis, individual SNPs are annotated with the specific trait, sample population or analysis method.
  
  Information on the following study-level fields is extracted:
  * Author (last name of first author)
  * Study date (online publication date, if available)
  * PubMed URL
  
negative.code: * Genes attributed to a SNP are extracted verbatim from the published report; "Intergenic" and "NR" (not reported) were used to denote a location which was not attributed to a particular gene (if it appeared that gene information was sought) or an absence of reporting on location information, respectively.
  
  === Quality control and SNP mapping
  
  An automated pipeline run at the NCBI performs checks for missing information, such as SNP identifiers, resolution of the citation in PubMed, existence of SNPs in dbSNP, confirmation of gene names vs. NCBI's Gene database, confirmation that the reported SNP and gene are in the same chromosomal region, as well as adding additional information such as the SNP's base pair and cytogenetic location in the current human genome reference assembly.
  This information is then used for queries and in the production of the karyotype diagram.
  