Types of Screening
Screening for disease detection is often categorized into the following four types:
- Mass screening: This form of screening is aimed at large population groups that vary widely in their risk of the disease. Screening for PKU is an example of mass screening detected at newborns. Screening for visual impairment in elementary schools is another example of mass screening. In both cases everyone in the group is screened regardless of the probability of having the disease or condition.
- Selective screening: This form of screening is applied only to groups at high risk for the disease .Screening for elevated blood lead levels among inner-city children is an example of selective screening. So is screening for tuberculosis among prison inmates. Selective screening would be expected to detect more potential cases of a given disease than mass screening because of the difference in risk profiles between the populations being screening. Selective screening is sometimes referred to as targeted screening.
- Multiphase screening: This type of screening employs multiple screening tests at the same time. Thus, it may be used to detect the possibility of more than one disease or condition. Paramilitary exams, for example, may use multiphase screening to test for possible diabetes, hypertension, and hearing impairment.
- Case finding: This type of screening occurs in a clinical setting when patients visit their physician (or other health provider) for general consultation or unrelated problems, and physician takes the opportunity to request one or more routine screening tests. Unlike mass or selective screening where individuals with abnormal test results are generally referred for follow-up, case finding places the responsibility for follow-up on the physician performing or supervising the screening test. Therefore, case finding is more likely to result in follow-up than other types of screening. Many individuals identified as having elevated blood pressure during a mass screening, for example, may not seek the recommended follow-up, but a physician finding elevated blood pressure during a routine examination will ordinary schedule additional tests. Examples of case finding include screening for cervical cancer using Pap tests, heart abnormalities using an electrocardiogram, weight changes using a calibrated scale, and diabetes using blood tests or urine samples. In addition, optometrists and ophthalmologists routinely screen patients for glaucoma. Case finding has been referred to as opportunistic screening.