Percentage of the study sample excluded from the 6-month fixed-window look-back cohort, by duration of look-back period, look-back approach (fixed-window or all-available), and type of coronary heart disease (CHD) history claims algorithm, Reasons for Geographic and Racial Differences in Stroke (REGARDS) Study, 1999–2007. Black bar segments represent the percentage of participants who were excluded for not meeting the coverage requirement and who reported having CHD. Light gray bar segments represent the percentage of participants who were excluded for not meeting the coverage requirement and who reported no CHD. Dark gray bar segments represent the percentage of participants who were excluded for having CHD Medicare claims and who reported CHD. White bar segments represent the percentage of participants who were excluded for having CHD Medicare claims and who reported no CHD. The base algorithm identified persons with CHD claims containing International Classification of Diseases, Ninth Revision (ICD-9), codes for myocardial infarction or ICD-9 and Current Procedural Terminology codes for coronary revascularization (see text for details). The expanded algorithm identified persons with CHD claims in the base algorithm or ≥1 inpatient or physician evaluation and management outpatient claim with ICD-9 codes 410–414.