Improving imputation in disease-relevant regions: lessons from cystic fibrosis

Comparison of the number of variants imputed and predicted imputation accuracy stratified by minor allele frequency using the hybrid vs. HRC reference panels. The number of single-nucleotide variants or SNVs (indels were excluded from the hybrid for a fair comparison with HRC) in a the CFTR region (chr7:117,110,017–117,318,718; hg19) and b chromosome 7 minus the CFTR region. Multi-allelic variants are counted as one occurrence. r2 is the predicted imputation accuracy. The hybrid reference improves the number of SNVs imputed over the HRC for both the CFTR region and the full chromosome 7 for variants with MAF？≥？1