The UIHO16 data item is derived using NAACCR*Prep based on the state and county at the time of diagnosis according to the PRCDA definition in the April 7, 2016 Federal Register.

Data analyses restricted to areas with health care services provided by the Indian Health Service (HIS) improve the accuracy of American Indian/Alaska Native (AI/AN) cancer statistics. IHS Purchased/Referred Care Delivery Areas (PRCDA) consist of counties which include all or part of an AI/AN reservation and any county or counties which have a common boundary with a reservation. This derived data item facilitates the production of the most accurate and reliable incidence rates for the American Indian/Alaskan Native population and assists CDC staff in responding to specific tribal data requests.