Screening tests are laboratory tests that are used to identify individuals with or at increased risk for a particular condition or disease before they may even be experiencing symptoms or realise they may be at risk. The information derived from these tests can be used to counsel patients about their risks or likelihood of developing the condition or disease. Screening tests also help to detect disease in its earliest and most treatable stages. Therefore, screening tests are most valuable when they are used to screen for diseases that are serious and treatable, so that there is a benefit to detecting the disease before symptoms begin. They should be sensitive - that is, able to correctly identify those individuals who have a given disease. A positive screening test often requires further testing with a more specific test, which can correctly exclude those individuals who do not have the given disease, in order to confirm a diagnosis. Many routine tests performed at regular health examinations fall into the screening category, such as cholesterol testing and cervical smears for women. Newborns are screened for a variety of conditions at birth.
A diagnostic test may be used for screening purposes, although a diagnostic test is generally used to confirm a diagnosis in an individual who usually has signs, symptoms, or other evidence of a particular disease.