Are you sure you're not referring to the INR? I believe normal PTT is 25-30 seconds. I think normal PT(not PTT) is somewhere between 0.9-1.5. And normal INR is between 2-3 therapeutically. We don' give Coumadin if unless the INR is less than 3 at our hospital. Maybe you misread the question????? Of course, everything varies depending on the lab running the test but it still should be pretty much standard range.
PTT is sometimes referred to as Anti Xa (read as "anti 10a"). I would have another look at the question if I were you.