This study looked at whether or not all x-rays obtained in primary care offices need to be over-read by a radiologist. The researchers found that the primary care clinicians were able to identify radiographs for which a second reading by a radiologist would not result in substantial changes in care.

The Journal of the American Board of Family Practice 17:256-263 (2004)

http://www.jabfp.org/cgi/content/abstract/17/4/256