anchor.diff:  
   Studies and associations are eligible for inclusion in the NHGRI GWAS catalog if they meet the following criteria:
   
  -. Include a primary GWAS analysis, defined as array-based genotyping and analysis of 100,000+ pre-QC SNPs selected to tag variation across the genome and without regard to gene content.
  -. GWAS data from published studies which are incorporated into new GWAS analyses are eligible, provided they meet the other criteria.
  -. Studies imputing sequencing data to genotyping arrays are eligible as long as the arrays include sufficient genome-wide coverage so that the post-imputation analysis meets the definition of a GWAS analysis, as described above.
  +* Include a primary GWAS analysis, defined as array-based genotyping and analysis of 100,000+ pre-QC SNPs selected to tag variation across the genome and without regard to gene content.
  +* GWAS data from published studies which are incorporated into new GWAS analyses are eligible, provided they meet the other criteria.
  +* Studies imputing sequencing data to genotyping arrays are eligible as long as the arrays include sufficient genome-wide coverage so that the post-imputation analysis meets the definition of a GWAS analysis, as described above.
   
   Studies and associations are excluded if:
  -. The study was published in a language other than English.
  -. SNPs assayed were limited to those in candidate genes.
  -. The study uses customized gene-based arrays without a clearly described GWAS backbone, including those selected to replicate published GWAS findings (e.g., Metabochip, Immunochip, etc.).
  -. Samples were assayed to measure somatic variation (e.g., in tumor samples).
  -. The study does not include any new GWAS data.
  +
  +* The study was published in a language other than English.
  +* SNPs assayed were limited to those in candidate genes.
  +* The study uses customized gene-based arrays without a clearly described GWAS backbone, including those selected to replicate published GWAS findings (e.g., Metabochip, Immunochip, etc.).
  +* Samples were assayed to measure somatic variation (e.g., in tumor samples).
  +* The study does not include any new GWAS data.
   
   Individual SNP-trait associations identified in eligible studies are included in the Catalog if they meet the following criteria:
  -. Statistical significance (SNP-trait p-value <1.0 x 10-5) in the overall (initial GWAS + replication) population.
  -.. If a study does not report a combined p-value, the p-value and effect size from the largest sample size will be reported as long as the initial and replication samples each show an association of p < 1.0 x 10-5.
  -.. If a study does not include a replication stage, significant SNPs from the discovery stage will be reported.
  -.. SNP-trait associations that are described as previously known at the time of publication and are statistically significant in the GWAS sample, but are not attempted for replication, are reported.
  -.. The most significant SNP from each independent locus is extracted
  +
  +* Statistical significance (SNP-trait p-value <1.0 x 10-5) in the overall (initial GWAS + replication) population.
  +* If a study does not report a combined p-value, the p-value and effect size from the largest sample size will be reported as long as the initial and replication samples each show an association of p < 1.0 x 10-5.
  +* If a study does not include a replication stage, significant SNPs from the discovery stage will be reported.
  +* SNP-trait associations that are described as previously known at the time of publication and are statistically significant in the GWAS sample, but are not attempted for replication, are reported.
  +* The most significant SNP from each independent locus is extracted
   
   === Data extraction
   
  
positive.code: "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)
  
negative.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
  