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Validation of a population screening questionnaire to assess prevalence of stroke
P G O'Mahony1, R Dobson, H Rodgers
1Department of Medicine, University of Newcastle, Newcastle upon Tyne, UK.
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.