Roaming through methodology. XVIII. Selection of control groups

: The selection of a valid control group is important in case control studies and has therefore generated a fair amount of discussion in the epidemiologic literature. The proposal of the study usually determines the type of control group that should be selected. It is possible to select population controls, hospital controls, friends or relatives of patients or a variant of these. Each method has specific advantages and disadvantages. Random-digit dialing can be used to select population controls by telephone. This method is a valuable alternative when no registry exists.