Dear OK:
Some urologists will begin looking at % free PSA when PSA reaches 2.5. In your situation it's a moot point anyway...a % free of 15% is totally inconclusive and doesn't point to anything. Probably of more concern is the continuing rise of your PSA, i.e. the velocity.
What is your urologist suggesting at this point...biopsy? Repeat PSA tests?
Tudpock