Compromise screening strategies for chronic disease

When the technology used to screen a large population for a chronic disease is potentially harmful in itself, it becomes necessary to consider alternative screening strategies. These alternatives are compromises, since although less people are exposed to the danger of the screening technology, some who would have benefited from the examination never receive it. A previously developed mathematical model for mass screening programs is used to evaluate one type of compromise screening strategy, namely, a two stage screening examination with the first stage a harmless, relatively inaccurate test and the second stage the more accurate, potentially harmful examination. The formulas are then used to calculate the effectiveness of a one stage screening examination for breast cancer using mammography, relative to a two stage screening examination for which the first stage measures the erythrocyte sedimentation rate and the second stage is a mammography examination. It is shown that the numerical values obtained are not too far from a conjecture made in an earlier paper. It is concluded that a two stage screening examination should be used in any program which uses mammography to screen a large population of asymptomatic women for breast cancer