Quiz 3, Module Case-control
3. Which of the following do you think are the best eligibility criteria for the controls?
- Controls should be residents of Epiville who have not been diagnosed with Susser Syndrome.
- Controls should be members of the Superfit Fitness Center who have been diagnosed with Susser Syndrome but have not consumed either EnduroBrick or Quench-It.
- Controls should be members of the Superfit Center for at least 6 months in the last 2 years and not be diagnosed with Susser Syndrome at the time of data collection.
Answer (a) —
incorrect:
While it is correct that controls should not have the diagnosis of Susser Syndrome, it is also essential that cases and controls come from the same source population. In this scenario, cases come from the population of people who attend Superfit Fitness Center, while controls come from the general population of Epiville. Since the exposures of interest are only available at the Superfit Fitness Center, selecting controls from the general Epiville population will artificially create an association between these exposures and the outcome, since the controls do not represent the exposure distribution of the source population giving rise to the cases. More simply, the controls under this scheme would not necessarily become cases if they were diagnosed with the disease, since cases are restricted to Superfit members.
Answer (b) —
incorrect:
Controls should not be diagnosed with Susser Syndrome. Additionally, since we are interested in the effects of exposure variables, we should not select our controls based on their exposure to EnduroBrick or Quench-It. Selection of controls must always be independent of exposure.
Answer (c) —
correct:
An important point is that controls should be classified as cases if they develop Susser Syndrome; in other words, controls should meet the eligibility requirements for cases except for their disease status.
