I'm studying to take my CPC exam. One prep question included an anesthesiologist medically directing a CRNA for general anesthesia for open pleura biopsy. The correct answers were 00540-QK for the medical direction and 00540-QX to indicate it is a medically directed service. My question is: I cannot find anywhere in the CPT 2010 anything about modifiers such as QK, QX, AA QZ. Please help me locate this information for similar questions to come. Thanks, Susan