Identifying veterans with acute strokes with high-specificity ICD-9 algorithm with VA automated records and Medicare claims data: a more complete picture.

Medicare claims data are available to Department of Veterans Affairs (VA) researchers to identify veterans with acute stroke. Our study sought to (1) ascertain whether additional acute stroke cases are identified with Medicare data and (2) assess the use of VA and Medicare inpatient automated data for assigning the stroke date. The study population was veterans living in Veterans Integrated Service Network 8 with an acute stroke diagnosis during fiscal year 2001. High-sensitivity and high-specificity algorithms were applied to VA data sets and matched with Medicare files. We confirmed acute stroke cases and index dates using the VA Computerized Patient Record System (CPRS). VA data identified 582 veterans with acute stroke, but Medicare claims data identified 201 more such veterans. CPRS confirmed 94% of the VA and 77% of the Medicare cases. The median difference between CPRS and automated index dates was 11 days for VA and 4 days for Medicare data. Use of both VA and Medicare data provides a more complete sample of veterans with acute stroke.