HCPCS Level II codes are alphanumeric medical procedure codes, primarily for non-physician services such as ambulance services and prosthetic devices,. They represent items, supplies and non-physician services not covered by CPT-4 codes (Level I). Level II codes are composed of a single letter in the range A to V, followed by 4 digits. Level II codes are maintained by the US Centers for Medicare and Medicaid Services (CMS). There is some overlap between HCPCS codes and National Drug Code (NDC) codes, with a subset of NDC codes also in HCPCS, and vice-versa. The CMS maintains a crosswalk from NDC to HCPCS in the form of an Excel file. The crosswalk is updated quarterly.
There are three important HCPCS Level 2 codes for digital mammograms that often used (G0202, G0204 and G0206). The original mammogram codes (film based mammograms) are CPT codes (77055, 77056, and 77057), so it would be easy to overlook the increasingly used digital mammogram codes that remain as HCPCS Level 2 codes if one did not know they existed (and possibly under-report mammogram statistics).