When casting a spell at a hostile target, there are effectively three things checked to see if the spell hits and how hard. The chance that you have to hit a hostile player or mob with a spell is dependent on the difference in your levels, and how much extra spell hit ability you have from talents, gear, or your race.
Shadow Priest PvP Spell Pen and Hit Rating - World of Warcraft Forums
In contrast to the other. Pattern of development of hyperprolactinemia after.