Example of Case Control Study Design

Kaiser Sigmoidoscopy Study

Lead Editor(s): Jeff Martin, MD

Case-Control Study Design Choices

Kaiser Research Division 1990 Design choices:

Sigmoidoscopy Study

The design is based on the primary study base of Kaiser membership over an 18-year period.

Colon cancer deaths 1971-1988: 1712

Subjects: All colon cancer deaths were identified and then the subset of those deaths that could have been detected by sigmoidoscopy.

Using incidence-density sampling meant that at the date of each eligible colon cancer death, 4 Kaiser members were selected at random as controls from the membership enrolled at that time (note that any one of these controls could theoretically have later become cases).

Study Protocol

Protocol: The medical records of all cases and controls were reviewed to determine if they had undergone a prior sigmoidoscopy, and, if so, whether it was for indication or just a screening test.

Predictor =screening sigmoidoscopy (not incl sigmoidoscopy for indication)


RESULTS: 8.8% of cases vs. 24.2% had prior screening sigmoidoscopy

The results showed an approximately 3-fold increase in risk of colon cancer death among those not screened.