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In the last ten years several reports using a variety of health data sets have shown a high proportion of racial misclassification for Northwest American Indians and Alaskan Natives (AI/ANs). The result of this has been an underestimation of the burden of various diseases among Northwest AI/ANs. To address health issues related to misclassification, the Northwest Tribal Epidemiology Center has developed the Northwest Tribal Registry (NTR), which contains a demographic data set of 135,060 Northwest AI/ANs, and which can be used for record linkage studies to ascertain accurate disease rates for Northwest AI/ANs. However, the Seattle Indian Health Board Registration contains a large number of Northwest AI/ANs, and it has not yet been incorporated into the NTR. To ascertain the degree of concordance between the NTR and SIHB Registration, we conducted a record linkage study linking these two files. RESULTS: Of the 23,337 entries in the SIHB Registration, only 7,005 (30%) linked or matched with the NTR, leaving 16,332 who were not matched. Among the SIHB-NTR matches, 1,597 (22.8%) were from Northwest tribes; among the SIHB-NTR non-matches, only 3,413 (20.9%) were from Northwest tribes. CONCLUSION: The NTR is missing information on a substantial number of AI/ANs who have utilized the Seattle Indian Health Board for health care services. However, less than a fourth of these individuals are from Northwest tribes served by the Northwest Portland Area Indian Health Board.

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Northwest Portland Area Indian Health Board, Portland, Oregon.