Risk Assessment II: Odds Ratio

lar setting), you can make reasonable assumptions about the size of the population, and thus make reasonable estimates of the true risk. What if you are suspicious that a particular exposure might increase the risk of developing a particular condition? Say you identify a group of patients with a cancer and wish to determine if a particular exposure is a risk factor. It would be impractical, particularly if you are dealing with a rare condition, and unethical, to expose disease-free individuals to the potential risk factor and measure the frequency of cancer development. You could, however, review the records of those with cancer and determine how many of them were exposed to the potential risk factor. You could then create a group of people otherwise similar, but without cancer, and determine the proportion of this group that was exposed to the potential risk factor. By performing this case-control study and comparing the proportion of those exposed with cancer (the cases) to those exposed but without cancer (the controls), you can gain insight into the risk factor’s association with the cancer. This comparison is typically presented as the odds ratio.