Hey,
currently, I am working on 454 sequencing data. I am using GATK to call SNPs and indels, which works relatively well for the SNPs with the recommended filtering options. However, I was interested to raise sensitivity, which is why I started experimenting with the QD value. I restarted the whole GATK pipeline (including the genotyping) with the filtering option "QD<0.0" instead of "QD<2.0". As I did not change any other parameters, I was just expecting to see more SNPs being called. However, I came across a list of SNPs, which did contain some new SNPs, but which was also lacking one of the previously called SNPs (it was not even present in the raw HaplotypeCaller output). How could this have happened?
This is an extract from the vcf file containing the SNP that was previously called:
4 106156187 rs17253672 C T 490.77 . AC=1;AF=0.500;AN=2;BaseQRankSum=2.341;ClippingRankSum=1.022;DB;DP=161;FS=4.193;MLEAC=1;MLEAF=0.500;MQ=60.00;MQ0=0;MQRankSum=-0.231;QD=3.05;ReadPosRankSum=1.347 GT:AD:DP:GQ:PL 0/1:10,12:22:99:519,0,262
I am very curious to hear whether anyone might have an explanation for my findings. Many thanks in advance!