Ask Dr. Z

We have had several cases (CCLV or EP) lately that have been cancelled or rescheduled due to labs being off. They made it as far in the department as the lab and then our pre-procedure area, where the nurse continues the process in prepping the patient (IV, consent, fluids, shaving etc.). Once the labs come back, we've had to reschedule or cancel the procedure. I was told that I should be coding the procedure with a -73 modifier. Is this correct? What would the appropriate situations be where this would apply, and does that cover any procedure under those circumstances?