From my experience, commercial non Medicare products use modifier 33 and Medicare products use modifier PT, make sure you've got the right modifier for the insurance billed. Also, most commercial products consider a personal history of polyps as diagnostic, not preventive, so patient out of pocket applies unless you're billing a routine screening.
From what I've seen, most insurances apply the patient out of pocket on any additional row because their edits indicate only 1 screening/preventive service is allowed per reporting period (so if you bill 45385, PT and 45384, 59 the 45384 gets copays/coins/ded). I have argued this point, sent letters, notes, etc. and they don't often change the reimbursement. Their logic is ok, the first polyp removed is covered as preventive, but now polyps exist and any subsequent removal of polyps by different technique is not routine.
I have tried putting the PT, 59 on the second procedure, but our claims scrubber kicks the row out because it wants to the 59 in the first modifier position. Then with the PT in the second position, I've received denials from the payer for multiple modifiers not recognized/supported.
Last case effort is to submit a clinical edit appeal form with notes explaining that multiple preventive procedures were performed and get the patient involved to help fight the payer's decision. They can contact member services with the DOS and codes and argue their preventive policy and get it overturned. The patient is their best advocate.
Good luck!
Ultimately, payer policies are between the patient and the payer and