It's possible, depending on when implantation occurred and how much hCG your body's producing. I'd go with one of the early response ones (the ones that specifically say they can be used up to 5 days before a missed period) just to be sure.
I was 18 dpo with my first (I knew before then because I was charting and knew for sure when I ovulated, but I wanted to wait to make sure it would show up on the test). I was 14 dpo with my second (I was pretty sure about a week before that, but figured I'd go ahead and test since my period didn't show).
at 12:45 PM on Aug. 14, 2010