I have in my prewarmed policy:

Pre-warming should be used very cautiously, as it may result in the removal of clinically significant antibodies as well. Also, the use of no enhancement also limits the detection of any underlying alloantibody. This technique must never be used to eliminate unidentified reactivity.

I also have in my antibody ID policy that you must first detect a cold reacting antibody and perform a gel panel before trying to "get rid" of the cold by prewarming.