The primary procedure 38525 is billed, which does NOT allow an assist, with the add-on code 38900, which does allow an assist. Do you bill the assist on 38900? My thought is CPT 38900 can be used with other CPT codes that do allow an assist and in that case you can add it. But when billed as an add-on where the primary procedure does NOT allow the assist, then you can't bill 38900 with an assist either. Just wondering what the opinion is.