Validity of Self-Reported Stroke: The Tromsø Study

Abstract

Background and Purpose —The aim of this study was to validate the diagnosis of self-reported stroke. Methods —During 1994–1995, 27 159 people attended a population health survey in the community of Tromsø, Norway, a response rate of 77%. A total of 418 attenders reported a history of stroke. In 1997, all individuals with a self-reported stroke who were still living in the community (n=362) were invited to a clinical reexamination. For each of the 269 people who were reexamined, a person who reported no history of stroke was selected and was reexamined in the same way. Results —On the basis of the reexamination, 213 (79.2%) of the self-reported strokes were confirmed. Thirteen individuals (4.8%) had a possible stroke. The remaining 43 individuals had either transient ischemic attack (TIA; n=18), traumatic head injuries (n=16), or perinatal cerebral damage, complicated migraine, syncope, possible TIA, or cerebral aneurysm without bleeding (n=9). Among the confirmed strokes, 30 (14.1%) were hemorrhagic and 118 (55.4%) were thromboembolic. Of the 30 hemorrhages, 16 were subarachnoidal bleedings, 10 due to ruptured aneurysms. The histories of stroke, including both the symptoms and the signs, often had a paucity of details and precision, making it impossible to classify 65 stroke victims (30.5%) into stroke subtypes. The positive predictive value (PPV) of a self-reported stroke was 0.79. The PPV was significantly ( P =0.016) greater in men (0.88) than in women (0.73). Individuals older than 60 years had a significantly greater PPV than those younger than 60 years (PPV 0.83 and 0.73, respectively; P =0.05). Hypertension was associated with a greater PPV, whereas a history of either ischemic heart disease, diabetes mellitus, lung disease, or depression had no impact on the PPV. The estimated sensitivity of self-reported stroke in the survey population was ≈80% and the specificity was 99%. Conclusions —We conclude that a self-administered questionnaire can be used to assess the prevalence of stroke in epidemiological research.