Thank you so much. Signatera uses your tissues to look for that specific dna in your bloodstream from what I understood. You can call either company to get more information and even request to speak with the genomic counselor. Guardant 855-698-8887 and Signatera is 650-489-9050. Guardant takes 2-3 weeks and Signatera takes about 5 weeks, the first time but I think only a couple of weeks after that.