About BaseQRankSum

Ken

Hi,

In some of my calls, I have ID=BaseQRankSum, whereas in others, it isn't reported. I'm wondering what makes the unified genotyper call this for some SNPs but not for others. Also, in the documentation, it says this test cannot be done on homozygous sites: "bases of the alternate allele). Note that the base quality rank sum test can not be calculated for homozygous sites."

But this value is present at 1/1 sites for the GT field, which I understand it to be homozygous calls? e.g.

BaseQRankSum not called: chr1 5503270 . G A 1023.62 . AC=2;AF=1.00;AN=2;DP=29;Dels=0.00;FS=0.000;HRun=0;HaplotypeScore=0.0000;MQ=56.06;MQ0=0;QD=35.30;SB=-375.13 GT:AD:DP:GQ:PL 1/1:0,29:29:87.24:1057,87,0

BaseQRankSum called: chr1 6577241 . G A 1359.86 . AC=2;AF=1.00;AN=2;BaseQRankSum=2.312;DP=43;Dels=0.00;FS=0.000;HRun=1;HaplotypeScore=0.0000;MQ=59.13;MQ0=0;MQRankSum=1.692;QD=31.62;ReadPosRankSum=0.787;SB=-641.06 GT:AD:DP:GQ:PL 1/1:3,40:43:34.37:1393,34,0

Can someone help interpret this?

Many thanks, Ken

ebanks

The documentation should really read: "Note that the base quality rank sum test can not be calculated for sites without a mixture of reads showing both the reference and alternate alleles." That should clarify things for you.