I received a request for an interview at Pitt without a secondary, interviewed there in late February, and got in. The staff there told me that they send out about 150 letters each year requesting interviews without a secondary. From what I've read on this forum, it's based primarily on numbers, but they do look at the rest of the AMCAS app as well. I thought my faculty interview went pretty poorly, so I was pleasantly surprised a few weeks later when I got in.