Factors in Determining Scope of Disease Screening

Screening

There are several criteria that can go into a decision to initiate screening for a disease. The disease that I have chosen as an example is colorectal cancer. The prevalence of the disease is one factor. Diseases with a relatively high prevalence are more likely to require screening, as mass screening for rare diseases is not necessarily a good use of funds.. Other consideration is the availability of reliable tests. In the case of colorectal cancer, this is a disease with relatively high prevalence, but also a number of reliable tests ranging from barium tests to colonoscopy.

The value of early detection is also an important variable. For something like ALS, the prognosis will not change with early detection, but with colorectal cancer the prognosis changes a lot if you find polyps, or even Stage 1 tumors. So setting up a screening program is important for diseases where there is high prevalence, where early detection matters, and where there are tests that can allow for early detection. In the case of colonoscopy or sigmoidoscopy, there are constraints with respect to the number of practitioners who are able to perform these tests, so the capacity constraints of testing will also play a role in the decision.

Once it has been decided that there will be a screening program, the next step is to consider what the population should be that will be targeted for the screening. The population should be those who are at most risk of the disease, however, there are other considerations at work, such as the consequences of not being screened. It is usually recommended, for example, that screening for colorectal cancer should be something everybody does after the age of 50, but is sometimes recommended for people with a family history of the disease. For people in these groups, screening programs are typically available. However, there is an ethical consideration here, because somebody who is not in one of those groups can still get colorectal cancer. Younger people who contract this disease will often die, because they will be asymptomatic until Stage 3, at which point their odds of survival are severely diminished. The screening is something that healthy people can easily deal with physically. While fewer detections will be made, the outcomes for those who do have the disease will improve substantially if they are brought into the screening program. The cost of screening such a large number of people who probably don't have the disease is often taken into consideration here.