The subject of screening stands at the intersection of medicine and public health and the law. Medicine is concerned about the care of the individual patient; public health focuses on maintaining and improving the health of entire populations. The law is concerned with the balance of rights and responsibilities, protecting society from errant individuals and protecting the individual from undue constraints of society.

In looking specifically at the questions of screening or testing for the Human Immunodeficiency Virus (HIV) it is useful to consider the meaning of the words “tests” and “screening” because many different terms are applied to these concepts — diagnostic testing, case finding, screening, surveillance, and so on. In all cases, medical tests have a common purpose: to provide information that sheds light on the probability that the disease of interest actually is present in the patient being tested.