The 2018 NASS applied updated versions of the HCUP Surgery Flag Software for Services and Procedures and the CCS for Services and Procedures Tool. As a result of the HCUP tool updates, the Current Procedural Terminology (CPT) procedures and CCS procedure groups defined as in-scope for the NASS sample changed slightly. Also, additional analyses revealed an inadequate capture of some procedures, because of an inability to obtain Level II HCPCS codes from all hospital-owned facilities in the sample. Percutaneous Transluminal Coronary Angioplasty (PTCA) CCS 45 was removed from the list of in-scope procedures in 2018.

A complete list of in-scope CCS procedure groups for each data year is included in Appendix B of the Introduction to the NASS on the NASS Database Documentation page on HCUP-US.