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摘要: Study DesignGenetic association studies typically use a case–control11 or a cohort12 design. In general, patients with stroke are ascertained when they present to the hospital or outpatient clinic. For individuals enrolled in prospective cohorts that do not require a particular diagnosis for entry, stroke cases become defined when they develop a stroke during follow-up. Regardless of the study design, cases and controls must be clearly and consistently defined.Cases should be patients who have had an ischemic stroke (IS) or hemorrhagic stroke: intracerebral hemorrhage (ICH) or subarachnoid hemorrhage (SAH). For IS and ICH, stroke is defined as a sudden onset of a focal neurological deficit consistent with a vascular cause and either confirmatory pathological or imaging evidence (computed tomography or MRI) and with other causes excluded. 13 Imaging or pathological confirmation is critical for genetic studies to distinguish between IS and ICH reliably. The diagnosis of aneurysmal SAH (aSAH) is based on the presence of extravasated blood in the basal cisterns on head computed tomography or MRI, or—if imaging is negative—by cerebrospinal fluid xanthochromia. For patients with normal brain imaging and xanthochromia, proof of an intracranial aneurysm (IA) is a prerequisite for inclusion as aSAH. Diagnosis of aSAH can also be made by autopsy. Controls should be clinically stroke free (brain imaging not required). They should be of similar sex, age, and race/ethnicity distribution as cases (minimal) and preferably ascertained from a comparable geographic region and over a similar time period as cases. Imbalances in vascular risk …