Multiphasic screening: an idea whose time has passed.

The theory of screening for preclinical disease requires that early diagnosis and treatment will lead to an outcome which is more favorable than that resulting when treatment is initiated after symptoms appear. In practice, this requirement is met for a surprisingly small number of diseases. Early detection components of "health packages" must be developed, therefore, strictly on the basis of proven effectiveness. Existing programs should be revised in accordance with international guidelines, and adapted as needed to the local incidence and prevalence of disease and anticipated population compliance, so that the maximum benefit of early detection can be realized and the numerous hazards of screening avoided.