How does self-reported history of stroke compare to hospitalization data in a population-based survey in New Zealand?

BACKGROUND AND PURPOSE There is mixed evidence concerning the validity of self-reported history of stroke in population-based studies. We aimed to examine the validity of self-reported stroke using hospitalization with a primary diagnosis of stroke as the reference group. METHODS Self-reported history of stroke was taken from the Survey of Families, Income, and Employment (N=18 950; 2004-2005) and defined as a respondent answering yes to the question, "Have you ever been told by a doctor that you have had a stroke?". Survey of Families, Income, and Employment respondents consented to link their data to the New Zealand Health Information Service records of publically funded hospitalizations between 1990 and 2006. We calculated positive predictive value, sensitivity, and specificity of self-reported stroke against hospitalization for stroke. RESULTS Approximately 2% of the adult Survey of Families, Income, and Employment population reported they had been told by a doctor that they had a stroke. Only 1% had evidence of hospitalization for stroke since 1990. The sensitivity of self-reported stroke was 73% and specificity was 98%. However, the positive predictive value, people who reported having a stroke with confirmation of hospitalization for stroke, was low at 29%. CONCLUSIONS The use of self-reported stroke will most likely overestimate the prevalence of stroke. A combination of methods is required to determine prevalence in population-based studies.