Verifying the stroke-free phenotype by structured telephone interview

Background and Purpose-Case-control, cohort, and twin studies support a gen etic contribution to ischemic stroke risk. Sibling pair linkage methods req uire identification of concordant or discordant siblings or both. We design ed and tested a structured telephone interview to verify the stroke-free ph enotype, Methods-A coordinator unaware of medical record data used an 8-item questio nnaire to conduct a structured telephone interview of 70 outpatients aged > 60 years. The questionnaire inquired about the sudden onset of deficits in strength, sensation, vision, and language. A subject was defined as stroke free by interview if responses to all items on the questionnaire were negat ive. Results of the telephone interview were compared with data obtained fr om a systematic medical record review (benchmark). Results-interview time was 5 minutes or less for all subjects. All subjects who began the interview completed it. Records were reviewed in all subject s. Medical record review detected ischemic stroke or transient ischemic att ack (TIA), or both, in 5 patients (7%). There were no significant differenc es in sex distribution or risk factor rates in patients who were designated stroke free or not stroke free by interview. Having 1 or more positive ite ms on the questionnaire was significantly associated with finding stroke (P <0.001), TIA (P<0.001), or either stroke or TIA (P<0.001), on medical recor d review. The telephone interview had a sensitivity of 1.0 (95% CI 0.48 to 1.0), specificity of 0.86 (95% CI 0.75 to 0.93), positive predictive value of 0.36 (95% CI 0.13 to 0.65), and negative predictive value of 1.0 (95% CT 0.94 to 1.0). Conclusions-Our instrument can identify the stroke-free individual with a h igh degree of confidence in a very efficient manner. It may be particularly suited for centralized verification of stroke discordancy in multicentered sib-pair genetic studies.