Designing multi-ethnic stroke studies: the Brain Attack Surveillance in Corpus Christi (BASIC) project.

The Brain Attack Surveillance in Corpus Christi (BASIC) project is a population-based stroke study comparing Mexican Americans and non-Hispanic whites. Extensive effort is made to detect all patients regardless of ethnicity and ensure equal participation in the interview among both groups. We describe here the study's design and process evaluation with a focus on reducing bias in case ascertainment and participation. During the first 28 months of the project, 11,829 subjects were screened. Availability of neuroimaging did not differ by ethnicity (P=0.22), nor did confidence in the validated diagnosis of stroke (P=0.10). Participation rate in the interview also did not differ by ethnicity (P=0.92). There was excellent agreement of ethnic classification between chart abstraction and self-report (kappa=0.94, P<0.001). We conclude that multi-ethnic stroke comparison studies are feasible. Utilizing epidemiologic principles to design, recruit and analyze data are critical. Process evaluation to examine for sources of bias is important to study conduct.