Genome-wide screen for stroke: Pilot testing in the Siblings With Ischemic Stroke Study (SWISS)

Analytic strategies for stroke genetics

Strokes occur in first-degree relatives of stroke patients at rates approximating 40%; estimated population prevalences range from 3%-12%. The recent discovery of the Strk1 gene in Icelandic families, associated with a 7-fold increased stroke risk in carriers, strongly implicates a genetic contribution to stroke independent of other genetically based risk factors such as hypertension or diabetes. In this article we review the evidence for genetic contributions to stroke. We describe roles for genetic and molecular epidemiology in evaluating this complex disease. We delineate study design issues and analytic strategies to determine genetic association.

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

BACKGROUND AND PURPOSE

We sought to determine pedigree availability for a concordant sibling pair study of genetic risk factors in ischemic stroke.

METHODS

Probands with confirmed ischemic stroke were prospectively enrolled. Family histories were obtained by systematic interview. A study neurologist prospectively assigned stroke subtype.

RESULTS

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.

CONCLUSIONS

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.

Validating the Questionnaire for Verifying Stroke-Free Status (QVSFS) by neurological history and examination

BACKGROUND AND PURPOSE

The Questionnaire for Verifying Stroke-Free Status (QVSFS) is an 8-item structured interview designed to identify stroke-free individuals. Previously, the QVSFS was validated with medical record review in a cohort with a low prevalence (7.1%) of stroke or transient ischemic attack (TIA). The objective of this study was to evaluate the validity of the QVSFS by comparing it with stroke status as determined by neurological history and examination in a population with a higher prevalence of stroke.

METHODS

A research assistant administered the QVSFS to outpatients from Veterans Administration stroke and general medicine clinics. Subjects were defined as QVSFS negative if responses to all 8 questions were negative. Questions requiring rephrasing or clarification were noted. Neurologists, blinded to QVSFS scores, interviewed and examined all subjects to determine stroke-free status, defined as no history or examination findings of previous stroke and/or TIA.

RESULTS

One hundred fifty-five subjects were examined; mean age was 70 years; 98.1% were male. Seventy-eight subjects were determined to be stroke free by the neurologist. The negative predictive value of the QVSFS was 0.96, with positive predictive value of 0.71. No question required rephrasing or clarification >5 times. Twenty-two subjects (14.2%) required rephrasing or clarification of at least 1 question.

CONCLUSIONS

The QVSFS can effectively identify stroke-free individuals with a high degree of accuracy, even in a population with a large proportion of patients with prior stroke or TIA. Accuracy for identifying subjects with stroke and/or TIA is lower, but the QVSFS may still be useful as a screening tool in that regard.