Association studies are used to define risk in unrelated individuals. Genetic markers are tested in unrelated cases of hypertension rather than family members. The frequency of a mutation or polymorphism is compared between hypertensive individuals and matched controls. Approximately 100 to 1000 cases and controls are required, depending on factors such as the frequency of the polymorphism, and the difference it is desirable to detect between groups [64]. There are risks in the case-control study design in that selection bias or unanticipated ethnic heterogeneity may give spurious results, and results should therefore be treated cautiously until replicated.
© 2001 Alexander Binder