This information is only used if you are coding an inpatient facility claim. I am not an inpatient facility coder, but I believe these are not actually coding instructions, but rather are information on how DRGs (diagnosis-related groups) are assigned to determine the severity of illness in order to calculate the hospital's reimbursement rates. CC is for comorbid conditions, and certain PDX (primary diagnosis) codes, when paired with those comorbidities, can change the DRG and result in higher payment for the hospital. If you are doing physician coding, these references can be disregarded. If you do take on a role as an inpatient coder, your facility or employer should give you training on the proper use of this information as pertains to their own payers and policies. Perhaps if there is anyone on the forum with inpatient experience, they will be able to explain this in a little more detail.