candidate region selection in an XP-EHH analysis

Question

[prasundutta87]

Hi,

In an XP-EHH analysis, whenever a high scoring peak is observed, it's a practice to capture the candidate region around the highest scoring SNP and check which genes are present. How many base pairs upstream and downstream should be checked? Different papers follow different values. What is the basis of this decision?

PS. I don't have information about my ancestral and derived allele. I am just trying to check signatures of positive selection and I am aware that I cannot comment on the direction of the selection. I just want to capture regions that show the signature, and explore the genes present in the region.