Selection of controls in case-control studies. II. Types of controls.

Types of control groups are evaluated using the principles described in paper 1 of the series, "Selection of Controls in Case-Control Studies" (S. Wacholder et al. Am J Epidemiol 1992;135:1019-28). Advantages and disadvantages of population controls, neighborhood controls, hospital or registry controls, medical practice controls, friend controls, and relative controls are considered. Problems with the use of decreased controls and proxy respondents are discussed.