In the public health paradigm, "testing," "screening," "case finding," "surveillance," and ''counseling" are relevant to understanding what constitutes a screening program. In the context of this report, testing is the application of a test or measurement to selected individuals for the purpose of identifying a disease or medical condition. The individuals might be selected for testing because there is a clinical reason or risk factors that suggest the presence of the condition. Screening generally refers to the application of a test to all individuals in a defined population. Screening is commonly instituted for the purpose of case finding—identifying a previously unknown or unrecognized condition in apparently healthy or asymptomatic persons and offering presymptomatic treatment to those so identified. Screening is also sometimes done for surveillance purposes: to monitor the incidence or prevalence of a disease in a defined population over time, or to compare the incidence or prevalence among different populations. Surveillance is an important public health activity, and is necessary for monitoring the impact of, and allocating resources to, prevention programs. Counseling is the communication process by which individuals and their family members are given information about the nature, risks, burden, and benefits of testing, and the meaning of test results.

This report concentrates on HIV screening for the purpose of identifying and treating individual pregnant women for their own health and preventing transmission of HIV to their infants, that is, case finding. Testing of selected individuals and screening for surveillance purposes are important efforts, but not directly related to the committee's charge.

Through the experience with public health screening programs, a series of characteristics of well-organized public health screening programs has evolved (Wilson and Jungner, 1968). The committee's summary of the relevant characteristics is as follows:

1. The goals of the screening program should be clearly specified and shown to be achievable.
2. The natural history of the condition should be adequately understood, and treatment or intervention for those found positive widely accepted by the scientific and medical community, with evidence that early intervention improves health outcomes.
3. The screening test or measurement should distinguish those individuals who are likely to have the condition from those who are unlikely to have it. Tests can be judged in terms of their sensitivity (proportion of actual cases found by the test to be positive), specificity (proportion of non-cases found to be negative),