It's not considered a catchup until you hit a limit.
So, you have $17,500 in 401(k). Note: not 12k & 5.5k.
Are you over the base $17,500 (for 2013)? No. No catch-up yet.
Are you over a plan-imposed limit? (ex. plan limits deferrals to 6% of pay, and person makes $100,000). No? No catch-up yet.
Have you failed the ADP test and this person needs a refund? No? No catch-up yet.
Are you over the 415 limit of $51,000 (for 2013) after profit sharing? (17,500 + 39,000 = 56,500) Yes!
You can now re-characterize up to $5,500 as a catch-up.