A new probability formula for surveys to substantiate freedom from disease
A new probability formula for surveys to substantiate freedom from disease
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DOI：
10.1016/s0167-5877(97)00081-0
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发表时间：
1998-02-06
影响因子：
2.6
通讯作者：
Baldock, FC
中科院分区：
文献类型：
--
作者：
Cameron, AR;Baldock, FC
证实无疾病的调查变得越来越重要，这是由于动物和动物产品国际贸易规则的变化，以及疾病根除和国家级认证计划的增加。为了提供必要的保证，这些调查必须有健全的理论基础。到目前为止，大多数调查都是基于这样的假设，即所使用的筛查测试是完美的（灵敏度和特异性都等于1），和/或研究人群是无限的。显然，这些假设几乎总是无效的。本文提出了一个新的计算发现患病动物的精确概率的公式，它考虑了不完全检验和有限的种群大小，但计算上不方便，并给出了一个计算简单的近似公式。使用这些公式的样本量的计算和分析的调查结果进行了讨论。一个计算机程序，“FreeCalc”，实现的公式是沿着与样本量计算的例子，为两种不同的情况。这些公式和计算机程序使调查样本量要求的精确计算和调查结果的精确分析成为可能。因此，可以最大限度地降低调查成本，调查结果将可靠地提供所需的证据水平。(C)1998年Elsevier Science B.V.
Surveys to substantiate freedom from disease are becoming increasingly important, This is due to the changes in rules governing international trade in animals and animal products, and to an increase in disease eradication and herd-level accreditation schemes. To provide the necessary assurances, these surveys must have a sound theoretical basis. Until now, most surveys have been based on the assumption that the screening test used was perfect (sensitivity and specificity both equal to one), and/or that the study population was infinite. Clearly, these assumptions are virtually always invalid. This paper presents a new formula that calculates the exact probability of detecting diseased animals, and considers both imperfect tests and finite population size, This formula is computationally inconvenient, and an approximation that is simpler to calculate is also presented. The use of these formulae for sample-size calculation and analysis of survey results is discussed. A computer program, 'FreeCalc', implementing the formulae is presented along with examples of sample size calculation for two different scenarios. These formulae and computer program enable the accurate calculation of survey sample-size requirements, and the precise analysis of survey results. As a result, survey costs can be minimised, and survey results will reliably provide the required level of proof. (C) 1998 Elsevier Science B.V.