In my state, CNA's are licensed so you would have to take a licensure exam. However, my hospital hires unlicensed PCT's that have usually completed 6-12 months of nursing school. So you will have to check in your area.
Somebody asked this on the CNA forum too. In my area, the professors tell nursing students that they can get CNA/PCT jobs in the hospital after the first semester, however I was just interviewed and was told that other students had applied without a CNA license and were not eligible for hire into a CNA position. Guess it all depends, but in my area, no you need to be certified.