I am getting Medicare denials for the use of AS when filing claims for a NP that first assists for a Neurosurgeon. Denials state inaccurate or need for different Modifier. I researched and found some info to use AS and 80. This combination also got denied. I have gotten info from other billers that they have no problem getting paid with the use of only AS. Another stated she had to use AS and 81. Any comments from other coders on this?