OVERVIEW

In 2023, the Indian Health Service (IHS) and Centers for Medicare and Medicaid Services (CMS) signed a data use agreement (DUA) to performa data match between IHS and CMS data. That initial DUA was extended to include 2019 through 2023 data. The goal of the data match is to identify the number of American Indians and Alaska Natives (AI/AN) from IHS registrants who are enrolled in Medicaid. This report provides the results from the data match for 2019, 2020, 2021, 2022, and 2023 data for each state and overall. The results are provided in the report below.[1]

METHODS

The IHS/CMS match included IHS registrants and T-MSIS (Transformed Medicaid Statistical Information System) data[2] for 2019- 2023. The IHS
registration data was matched with T-MSIS Medicaid beneficiary data to determine how many American Indian/ Alaska Native IHS registrants were enrolled in Medicaid for 2019, 2020, 2021, 2022, and 2023. The match was performed using the last four digits of a patient’s social security number, birthdate, sex, state, up to the first five characters of the patient’s first name, middle initial, and up to the last eight characters of the patient’s last name. The IHS/CMS data match was performed by Health Apt[3]. Once the match was complete, the data was downloaded to the Virtual Data Resource Center (VRDC) where Dr. Rochelle Ruffer from National Indian Health Board (NIHB) accessed the data to analyze it.

LIMITATIONS

These results are a first step toward obtaining data on American Indian/Alaska Native Medicaid enrollment. The data provided from the match includes the count of American Indians/Alaska Natives who were enrolled in Medicaid and part of the IHS registrant. Note that CMS uses calendar year for their data and IHS uses Fiscal Year. Thus, there are some discrepancies with the reported data. In addition, the data provided in the VRDC did not include claims data. Thus, this report does not have any analysis of health outcomes of American Indians/Alaska Natives.

ACKNOWLEDGEMENTS

This IHS/CMS data match represents a milestone in Tribal public health. For the first time, thanks to the data match efforts across federal agencies, NIHB has access to data on Medicaid enrollment for American Indian/Alaska Natives. Thank you to everyone from IHS and CMS, including colleagues at ResDAC who helped to make this data match a reality. We look forward to future collaborations.

A summary of these results was briefly presented to the Tribal Technical Advisory Group (TTAG) data subcommittee on July 21, 2025, as part of the in- person TTAG meeting. In addition, a more extensive presentation was provided to the TTAG data subcommittee meeting on August 26, 2025. The feedback is much appreciated. NIHB colleague, Jeannie Le, provided both invaluable technical support as well as conversation about the presentation and interpretation of the data. NIHB will present the report to TTAG during their in-person meeting on November 12, 2025.

This publication was supported by the Centers for Medicare and Medicaid Services (CMS) of the U.S. Department of Health and Human Services (HHS) as part of a financial assistance award with 100 percent of the funding by CMS/HHS. The contents are those of the author and do not necessarily represent the official views of, nor an endorsement, by CMS/HHS, or the U.S. Government.