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I am using bedtools to test whether a set of variant calls produced by a new method is missing any variants from a set of known validated variants.

bedtools intersect -v -a newcalls.vcf -b goldstandard.vcf

It's working as intended for SNV calls, but it occasionally misses indels due to a single base pair discrepancy. It's usually an alignment artifact that doesn't affect the interpretation of the variant.

My first thought was to make a BED file with intervals that extend a few bp beyond each variant call, and comparing this BED file to the known variants. However, I was wondering whether approximate matching is possible with bedtools intersect?

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You can use bedtools intersect but first use bcftools norm. bcftools norm will left-align and normalize indels to get both vcf files consistent with each other. This should resolve the matching if they are truly matching variants.

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  • $\begingroup$ This could resolve some of the cases if the input files are not normalized. However, there could be indels that are normalized and 1 bp away from each other (i.e. close but not touching each other). In my understanding, the OP wants to consider these cases as genuine matches. $\endgroup$ – dariober Jan 7 '18 at 10:13
  • $\begingroup$ I will let the OP clarify but it seemed to me that these were matching variants just with alignment artifacts. If that is true then they should normalize out. $\endgroup$ – Bioathlete Jan 7 '18 at 14:19
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You could use bedtools closest with -d option (-d: In addition to the closest feature in B, report its distance to A as an extra column.). Indels that have no match in file A would be those where the closest indel in file B is more than x bases away.

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  • $\begingroup$ You have to be careful here that you are not matching a snp with an indel or vise versa. $\endgroup$ – Bioathlete Jan 7 '18 at 14:20

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