Feasibility of an affected sibling pair study in ischemic stroke: results of a 2-center family history registry.

We sought to determine pedigree availability for a concordant sibling pair study of genetic risk factors in ischemic stroke. Probands with confirmed ischemic stroke were prospectively enrolled. Family histories were obtained by systematic interview. A study neurologist prospectively assigned stroke subtype. Of 310 probands (median age, 75 years; range, 26 to 97 years; 48% women), 75% had at least 1 living sibling; 10%, at least 1 concordant living sibling; 2%, at least 1 concordant sibling living in the same city; and 7%, at least 1 concordant living and 1 discordant living sibling. Likelihood of having a concordant sibling increased significantly with proband age, even after adjustment for sibship size (P=0.002). Positive family history of stroke was not related to either proband stroke subtype or risk factor profile. Approximately 10 probands were screened to find 1 potentially concordant living sibling. A concordant sibling pair study should be multicentered and enable enrollment of siblings from diverse geographic areas.