Screening to control infectious diseases: evaluation of control programs for gonorrhea and syphilis.

Gonorrhea and syphilis serve as models for the definition of criteria for the evaluation of screening programs for detection of disease. Mass screening and selective screening are distinguished from individual screening (case finding). Important characteristics of screening tests are sensitivity, specificity, efficiency, precision, accuracy, and acceptability. Program evaluation includes process evaluation and outcome evaluation. Major criteria to consider in the evaluation of mass screening programs are prevalence and incidence of disease, predictive value of tests used, yield, available screening tests, acceptance, follow-up services, costs and benefits, and control over the spread of infection. All forms of screening programs should be evaluated by available methods so that they will operate with maximal efficiency and so that nonproductive programs can be discarded.