Evaluating linked ICD-10 Medicare claims data as a method of dementia case ascertainment in research settings

INTRODUCTION: US Medicare claims can be used to identify dementia cases for research. Our objective was to evaluate the performance of International Classification of Diseases, 10th Revision (ICD-10) code definitions versus research-based dementia ascertainment. METHODS: Participants of five Rush Alzheimer's Disease Center (RADC) cohorts with study visits between October 2015 and December 2019 and fee-for-service Medicare contributed observations. For each observation, we compared research-based dementia status to dementia status based on six ICD-10 code definitions. RESULTS: A total of 1869 participants contributed 5309 observations (mean age 82.9 years, 21.0% Black, 9.3% met research-based dementia criteria). The accuracy of ICD-10 code definitions was high (87%–90%); five of six code definitions favored specificity over sensitivity. All ICD-10 code definitions were less accurate among subgroups defined by older age, minoritized race, increased depressive symptoms, and history of stroke. DISCUSSION: Performance of ICD-10 code definitions mirrored that of ICD-9 code definitions. Awareness of differential performance by participant characteristics can improve the robustness of research. Highlights: We report the performance of the International Classification of Diseases, 10th Revision (ICD-10) code versus research-based dementia ascertainment. ICD-10 performed worse with age, depressive symptoms, minoritized race, and stroke. Awareness of accuracy and differential performance can improve research robustness.