VariantFiltration: how to filter samples where less then 95% of reads agree with the called genotype
I've been looking over the documentation for VariantFilteration and jexl (http://gatkforums.broadinstitute.org/gatk/discussion/1255/using-jexl-to-apply-hard-filters-or-select-variants-based-on-annotation-values) to figure out how to do this, but I can seem to find an answer.
I would like to filter snips where there are many reads that disagree with the called genotype (eg FORMAT 1:20,60:80:99:1900,0).
In pseudo code, I'd like to write something like "AD[GT]/DP<0.95", where the allelic depth (AD) for the called genotype (GT) divided by the total depth (DP) < 0.95. However, the docs indicate that it is not possible to access GT:
"For now, you can filter based on most fields as normal (e.g. GQ < 5.0), but the GT (genotype) field is an exception"
Is there another way to accomplish what I want using VariantFiltration? It seems like a common sense filter, and it's also something I frequently see in the literature for snips in haploid organisms.