VALIDATION OF A POPULATION SCREENING QUESTIONNAIRE TO ASSESS PREVALENCE OF STROKE

Background and Purpose A cross-sectional survey is the best method for determining the prevalence of a chronic condition such as stroke. Before embarking on a large population study, a valid screening instrument is necessary, This study aimed to validate a self-completion postal screening questionnaire for assessing lifetime history of stroke. Methods A random sample of 2000 people aged 45 years and over was selected from the Family Health Services Authority register. A brief self-completion questionnaire requesting self-reported history of stroke was mailed to each individual. Responders reporting a history of stroke received a request for a standardized home assessment visit. Confirmation of the diagnosis of stroke was made based on information from the home visit together with multiple sources of case ascertainment. False-negative responses and assessment of nonresponse bias were documented. Results The response rate for the questionnaire was 88%. Of the sample, 120 (6%) who were wrongly registered were excluded; 173 (10%) of the 1663 responders reported a history of stroke. The question ''Have you ever had a stroke?'' had a sensitivity of 95% and a specificity of 96%. Conclusions This simple self-completion questionnaire is a valid means of screening for cases of stroke in the community and could form the basis for subsequent studies of prevalence and health needs.