Background and Purpose--Rapid and accurate evaluation of stroke subtypes is crucial for optimal treatment and outcomes. This study assessed factors associated with the likelihood of an "ill-defined" diagnosis for stroke hospitalizations.

Methods--We examined all hospital claims for stroke among Medicare beneficiaries aged 65 years in 2000. Stroke subtypes included hemorrhagic (International Classification of Diseases, Ninth Revision, Clinical Modification codes 430 to 432), ischemic (433 to 434), ill-defined (436 to 437), and late effects of cerebrovascular disease (438).

Results--Among 445 452 hospital claims for stroke, 65.3% were ischemic, 20.9% were ill defined, 11.9% were hemorrhagic, and 1.9% were late effects of cerebrovascular disease. After controlling for age, women (odds ratio [OR],1.30; 95% CI, 1.28 to 1.32), blacks (OR, 1.31; 95% CI, 1.28 to 1.33), and Hispanics (OR, 1.27; 95% CI, 1.20 to 1.34) were more likely to receive a discharge diagnosis of ill defined compared with men and whites, respectively. Differences in age, sex, emergency room presentation, and evidence of diagnostic procedures accounted for some but not all racial disparities. In 14 states, ill-defined strokes constituted 25% of all stroke diagnoses.

Conclusion--The high proportion of stroke patients who receive an ill-defined diagnosis on discharge suggests a continued need for improvements in early response and prompt evaluation of strokes. Findings of geographic, gender, and racial disparities in ill-defined stroke diagnosis warrant further investigation. Reimbursement practices and public health efforts that promote hospital stroke policies are critical to improve disease reporting as well as clinical outcomes.