Mass screening

Mass screening, more simply called screening, is defined in health care as "organized periodic procedures performed on large groups of people for the purpose of detecting disease." The goal of screening is the primary prevention, "the prevention of disease or mental disorders in susceptible individuals or populations", of disease.

When is mass screening justified?

According to World Health Organization guidelines published in 1968:

1. The condition should be an important health problem.
2. There should be a treatment for the condition.
3. Facilities for diagnosis and treatment should be available.
4. There should be a latent stage of the disease.
5. There should be a test or examination for the condition.
6. The test should be acceptable to the population.
7. The natural history of the disease should be adequately understood.
8. There should be an agreed policy on who to treat.
9. The total cost of finding a case should be economically balanced in relation to medical expenditure as a whole.
10. Case-finding should be a continuous process, not just a "once and for all" project.

Simpler criteria have been proposed:

1. How great is the burden of suffering caused by the condition?
2. How good is the screening procedure in terms of accuracy, cost, acceptability?
3. If the condition is found, how effective is the ensuing treatment in terms of efficacy and patient compliance compared to waiting for later treatment.

Ideally, the evidence supporting these criteria comes from randomized controlled trials that show an improvement in the population's health when the proposed screening program is compared to no screening.

Although lesser study designs may provide preliminary support, a randomized controlled trial reduces the chance of lead time bias or length time bias affecting conclusions.