The concept of a screening procedure that can identify individuals in the early or presymptomatic stages of disease has been discussed for some years. Wilson and Jungner have presented a comprehensive review of the subject of screening and an appraisal of the current state of knowledge.
Screening has been defined as "the presumptive identification of unrecognized disease or defect by the application of tests, examinations, or other procedures which can be applied rapidly. Screening tests sort out apparently well persons who probably have a disease from those who probably do not. A screening test is not intended to be diagnostic. Persons with positive or suspicious findings must be referred to their physicians for diagnosis and necessary treatment." Screening is intended to be rapid and relatively inexpensive, and, as the authors say, it implies "a relatively simple (though not necessarily unsophisticated) method of case finding."
In this day of existing excessive