Diagnostic and screening tests may have risks such as misdiagnosis, as well as the potential benefits of correct diagnosis. Effective communication of this risk to both clinicians and patients can be problematic. The purpose of this study was to develop a metric called the “efficiency index” (EI), defined as the ratio of test accuracy and inaccuracy, or the number needed to misdiagnose divided by number needed to diagnose. This was compared with a previously described “likelihood to be diagnosed or misdiagnosed” (LDM), also based on “numbers needed” metrics. Datasets from prospective pragmatic test accuracy studies examining four brief cognitive screening instruments (Mini-Mental State Examination; Montreal Cognitive Assessment; Mini-Addenbrooke’s Cognitive Examination, MACE; and Free-Cog) were analysed to calculate values for EI and LDM, and to examine their variation with test cut-off for MACE. EI values were also calculated using a modification of McGee’s heuristic for the simplification of likelihood ratios to estimate percentage change in diagnostic probability. The findings indicate that EI is easier to calculate than LDM and, unlike LDM, may be classified either qualitatively or quantitatively in a manner similar to likelihood ratios. EI shows the utility or inutility of diagnostic and screening tests, illustrating the inevitable trade-off between diagnosis and misdiagnosis. It may be a useful metric to communicate risk in a way that is easily intelligible for both clinicians and patients.

中文翻译：

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向患者传达风险：为诊断和筛查测试制定“效率指数”

诊断和筛查测试可能存在误诊等风险，以及正确诊断的潜在好处。与临床医生和患者有效沟通这种风险可能存在问题。这项研究的目的是开发一种称为“效率指数”（EI）的指标，定义为测试准确率和不准确率的比率，或者误诊所需的数量除以诊断所需的数量。这与之前描述的“被诊断或误诊的可能性”（LDM）进行了比较，同样基于“需要的数字”指标。来自前瞻性语用测试准确性研究的数据集分析了四种简短的认知筛查工具（迷你精神状态检查；蒙特利尔认知评估；迷你阿登布鲁克认知检查，MACE；和 Free-Cog），以计算 EI 和 LDM 的值，并用 MACE 的测试截止检查它们的变化。EI 值也使用改进的 McGee 启发式方法计算，以简化似然比以估计诊断概率的百分比变化。研究结果表明，EI 比 LDM 更容易计算，并且与 LDM 不同，EI 可以以类似于似然比的方式进行定性或定量分类。EI 显示了诊断和筛查测试的有用或无用，说明了诊断和误诊之间不可避免的权衡。以临床医生和患者都容易理解的方式传达风险可能是一个有用的指标。EI 值也使用改进的 McGee 启发式方法计算，以简化似然比以估计诊断概率的百分比变化。研究结果表明，EI 比 LDM 更容易计算，并且与 LDM 不同，EI 可以以类似于似然比的方式进行定性或定量分类。EI 显示了诊断和筛查测试的有用或无用，说明了诊断和误诊之间不可避免的权衡。以临床医生和患者都容易理解的方式传达风险可能是一个有用的指标。EI 值也使用改进的 McGee 启发式方法计算，以简化似然比以估计诊断概率的百分比变化。研究结果表明，EI 比 LDM 更容易计算，并且与 LDM 不同，EI 可以以类似于似然比的方式进行定性或定量分类。EI 显示了诊断和筛查测试的有用或无用，说明了诊断和误诊之间不可避免的权衡。以临床医生和患者都容易理解的方式传达风险可能是一个有用的指标。EI 显示了诊断和筛查测试的有用或无用，说明了诊断和误诊之间不可避免的权衡。以临床医生和患者都容易理解的方式传达风险可能是一个有用的指标。EI 显示了诊断和筛查测试的有用或无用，说明了诊断和误诊之间不可避免的权衡。以临床医生和患者都容易理解的方式传达风险可能是一个有用的指标。