Ozonoff David
Department of Environment Health, Boston University School of Public Health, Boston, MA 02118, USA.
Int J Occup Med Environ Health. 2004;17(1):35-41.
An important part of the Precautionary Principle is that taking action is justified for protecting public health even when there is some scientific uncertainty. We examine here the two components of this central feature of the precautionary principle, scientific uncertainty and decision making. In order to operationalize the principle we should examine the consequences of its decision rules and how they perform under various conditions. The performance of decision rules in disease screening is measured by the sensitivity and specificity of the rule, but the consequences for the patient are given by the positive and negative predictive values, determined not only by the performance of the rule but the prevalence of the disease in the population. We look at positive and negative predictive value of the Precautionary Principle from the standopoint of the costs to one or other parts of society, show that the usual rule which tends to maximize sensitivity in favor of specificity may have unexpected consequences, and demonstrate that it is sometimes possible to trade sensitivity and specificity off against each other in a way that improves both positive and negative predictive value, or worse, degrades both.
预防原则的一个重要部分是，即使存在一些科学上的不确定性，为保护公众健康而采取行动也是合理的。我们在此审视预防原则这一核心特征的两个组成部分，即科学不确定性和决策制定。为了实施这一原则，我们应当考察其决策规则的后果以及它们在各种条件下的表现。疾病筛查中决策规则的表现通过该规则的灵敏度和特异度来衡量，但对患者的影响则由阳性预测值和阴性预测值体现，它们不仅取决于规则的表现，还取决于人群中疾病的患病率。我们从对社会某一方或另一方的成本角度审视预防原则的阳性和阴性预测值，表明通常倾向于在牺牲特异度的情况下最大化灵敏度的规则可能会产生意想不到的后果，并证明有时可以以一种同时提高阳性和阴性预测值，或者更糟的是，同时降低两者的方式来权衡灵敏度和特异度。
