Certified in Public Health (CPH) Practice Exam

In a case-control study of pancreatic cancer, what aspect could render the conclusions drawn about diabetes inaccurate?

1. The study had matched controls properly.

2. Diabetes was not common enough in the control group.

3. Failure to establish the time sequence between diabetes onset and cancer diagnosis.

4. All diabetic subjects were included in the study.

The correct answer is: Failure to establish the time sequence between diabetes onset and cancer diagnosis.

The aspect that could render the conclusions drawn about diabetes inaccurate in a case-control study of pancreatic cancer is related to the failure to establish the time sequence between diabetes onset and cancer diagnosis. This is crucial because in epidemiological studies, understanding the temporal relationship helps clarify whether diabetes could be a risk factor for pancreatic cancer or if it might be a consequence of the cancer itself. If researchers cannot determine when the diabetes occurred in relation to the cancer diagnosis, it becomes challenging to draw meaningful conclusions about causation. For example, if diabetes develops as a symptom or consequence of pancreatic cancer, then it would not be appropriate to consider it a risk factor. This temporal clarity is essential for establishing a proper causal link between conditions, which is a primary goal in case-control studies analyzing potential risk factors for diseases like pancreatic cancer. While matching controls, prevalence of diabetes in the control group, and inclusion of diabetic subjects are all important methodological considerations, they do not directly address the key issue of timing, which is fundamental in understanding the actual relationship between diabetes and pancreatic cancer.