likelihood ratio

似然比
  • 文章类型: Journal Article
    牛结核病(bTB)对公众和动物健康构成了全球挑战,但其诊断仍存在一些不足。这项研究旨在根据WOAH指南评估单个皮内结核菌素测试(SIT)和验尸检查对不同诊断目标的准确性。评估了来自59只微生物培养物/PCR阳性牛和58只微生物培养物/PCR阴性牛的组织样品。诊断的敏感性和特异性,对于不同的预测试概率,估计了每种技术的阳性和阴性概率指数以及阳性和阴性预测值(PPV和NPV).严格解释的SIT在确认历史上没有bTB的人群中没有感染方面表现出中等精确度,假阳性率为12.1%,而且在根除计划的早期阶段也检测到阳性动物,假阴性率为13.6%。在预测试概率(PTP)低于42%的动物中,排除bTB的诊断性能显著高(NPV>90%)。验尸构成了一种有趣的替代工具,可以确认SIT的可疑和阳性病例,特别是在bTB患病率超过19%的地区,实施SIT和根除措施可能不切实际。在这些地区,患有结核病样病变的动物受到该疾病影响的可能性超过90%。同样,在PTP低于25%的牛群中,bTB的缺失可以自信地排除,超过90%的确定性。这些发现强调了SIT和事后检查的有效性,作为当前根除计划和在分子技术可能不可行的高流行地区控制bTB的有价值的技术。
    Bovine tuberculosis (bTB) constitutes a global challenge for public and animal health with still some deficiencies regarding its diagnosis. This study aimed to estimate the accuracy of the single intradermal tuberculin test (SIT) and post-mortem inspection for different diagnostic objectives following WOAH guidelines. Tissue samples from 59 microbiological culture/PCR-positive and 58 microbiological culture/PCR-negative cattle were evaluated. The diagnostic sensitivity and specificity, the positive and negative probability indices as well as the positive and negative predictive values (PPV and NPV) of each technique were estimated for different pretest probabilities. The SIT with strict interpretation demonstrated moderate precision in confirming the absence of infection in populations historically free of bTB, with a 12.1% rate of false positives, but also detecting positive animals in the early stage of the eradication programs, with a 13.6% rate of false negatives. The diagnostic performance for ruling out bTB was notably high (NPV > 90%) in animals with a pre-test probability (PTP) below 42%. Post-mortem inspection constituted an interesting alternative tool to confirm suspected and positive cases for SIT, particularly in areas with bTB prevalence exceeding 19%, where implementing SIT and eradication measures may be impractical. In these areas, the likelihood that animals with tuberculosis-like lesions are affected by the disease surpasses 90%. Similarly, in herds with a PTP below 25%, the absence of bTB could be confidently ruled out with over 90% certainty. These findings highlight the effectiveness of SIT and post-mortem inspection as valuable techniques for current eradication programs and controlling bTB in high-prevalence areas where molecular techniques may not be feasible.
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  • 文章类型: Journal Article
    自1960年代以来,有人呼吁在个案工作条件下对法医语音进行经验验证。自2000年左右以来,越来越多的研究人员和从业人员在似然比框架内进行法医语音比较研究和案例工作。近年来,这个研究人员和从业人员社区在案例工作条件下的验证方面取得了实质性进展,成为实践的标准部分:已经开发了进行验证的程序,以及用于表示结果的图形和度量,越来越多的论文正在发表,其中包括在反映案例工作条件的条件下对法医语音比较系统进行实证验证。一个悬而未决的问题,然而,是:在案例的上下文中,鉴于法医语音比较系统的经验验证结果,如何决定该系统是否足以将其输出用于法庭?本文提供了针对此问题的共识声明。贡献者包括具有在研究和/或案例工作环境中验证法医语音比较系统的知识和经验的个人,以及实际向法院提交验证结果的个人。他们还包括可以对这些问题提出法律观点的个人,以及具有更广泛的法医学验证知识和经验的个人。我们就从业者在进行评估和验证时应做什么提供建议,以及他们应该向法庭提出什么。虽然我们的重点明确是法医语音比较,我们希望这一贡献将引起更广泛关注法医学验证的听众的兴趣。虽然不是专门为法律观众写的,我们希望这项贡献仍然会引起律师的兴趣。
    Since the 1960s, there have been calls for forensic voice comparison to be empirically validated under casework conditions. Since around 2000, there have been an increasing number of researchers and practitioners who conduct forensic-voice-comparison research and casework within the likelihood-ratio framework. In recent years, this community of researchers and practitioners has made substantial progress toward validation under casework conditions becoming a standard part of practice: Procedures for conducting validation have been developed, along with graphics and metrics for representing the results, and an increasing number of papers are being published that include empirical validation of forensic-voice-comparison systems under conditions reflecting casework conditions. An outstanding question, however, is: In the context of a case, given the results of an empirical validation of a forensic-voice-comparison system, how can one decide whether the system is good enough for its output to be used in court? This paper provides a statement of consensus developed in response to this question. Contributors included individuals who had knowledge and experience of validating forensic-voice-comparison systems in research and/or casework contexts, and individuals who had actually presented validation results to courts. They also included individuals who could bring a legal perspective on these matters, and individuals with knowledge and experience of validation in forensic science more broadly. We provide recommendations on what practitioners should do when conducting evaluations and validations, and what they should present to the court. Although our focus is explicitly on forensic voice comparison, we hope that this contribution will be of interest to an audience concerned with validation in forensic science more broadly. Although not written specifically for a legal audience, we hope that this contribution will still be of interest to lawyers.
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  • 文章类型: Guideline
    证据的价值主要取决于命题。在旨在就评估和命题制定的困难方面向社区提供建议的两篇论文中的第二篇中,我们主要关注活动层面的命题。这有助于法院解决“个人的细胞材料是如何到达那里的?”的问题。为了做到这一点,我们扩展了第一篇配套论文中概述的框架。首先,重要的是不要混淆结果和主张。给定活动级别命题的陈述旨在帮助解决间接与直接转移的问题,以及活动的时间,但重要的是要避免在命题中使用“转移”一词。这是因为命题是由法院评估的,但是DNA转移是科学家解释其结果需要考虑的因素。理想情况下,在了解结果之前设置合适的活动水平命题,并解决以下问题:X刺伤Y与一个不知名的人刺伤了Y,但X在前一天遇到了Y。科学家分配证据的概率,如果每个备选命题都是真的,得出似然比。要做到这一点,科学家问:a)“如果每个命题都是真实的,那么期望是什么?”b)“有什么数据可以帮助评估命题的结果?”科学家在命题层次结构框架内工作。为DNA谱计算的证据价值不能转移到层次结构中的更高层级-给定子来源的计算,源和活动水平命题都是分开的。提供了一些例子来说明所支持的原则,以及此类评估应达到的标准。理想情况下,为了分配概率,分析师应该拥有/收集与案件相关的数据。这些数据必须与手头的案件相关,我们鼓励进一步研究和收集数据以形成知识库。贝叶斯网络对于帮助我们思考问题非常有用,因为它们迫使我们以合乎逻辑的方式考虑所有相关的可能性。提供了一个示例。
    The value of the evidence depends critically on propositions. In the second of two papers intended to provide advice to the community on difficult aspects of evaluation and the formulation of propositions, we focus primarily on activity level propositions. This helps the court address the question of \"How did an individual\'s cell material get there?\". In order to do this, we expand the framework outlined in the first companion paper. First, it is important not to conflate results and propositions. Statements given activity level propositions aim to help address issues of indirect vs direct transfer, and the time of the activity, but it is important to avoid use of the word \'transfer\' in propositions. This is because propositions are assessed by the Court, but DNA transfer is a factor that scientists need to take into account for the interpretation of their results. Suitable activity level propositions are ideally set before knowledge of the results and address issues like: X stabbed Y vs. an unknown person stabbed Y but X met Y the day before. The scientist assigns the probability of the evidence, if each of the alternate propositions is true, to derive a likelihood ratio. To do this, the scientist asks: a) \"what are the expectations if each of the propositions is true?\" b) \"What data are available to assist in the evaluation of the results given the propositions?\" When presenting evidence, scientists work within the hierarchy of propositions framework. The value of evidence calculated for a DNA profile cannot be carried over to higher levels in the hierarchy - the calculations given sub-source, source and activity level propositions are all separate. A number of examples are provided to illustrate the principles espoused, and the criteria that such assessments should meet. Ideally in order to assign probabilities, the analyst should have/collect data that are relevant to the case in question. These data must be relevant to the case at hand and we encourage further research and collection of data to form knowledge bases. Bayesian Networks are extremely useful to help us think about a problem, because they force us to consider all relevant possibilities in a logical way. An example is provided.
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  • 文章类型: Evaluation Study
    OBJECTIVE: Differing threshold levels of hepatitis B virus (HBV) DNA and alanine aminotransferase (ALT) are recommended by international guidelines for commencement of antiviral therapy. These guidelines advocate therapy for patients with significant fibrosis (METAVIR score ≥F2); we assessed the accuracy of these guideline-defined thresholds in identifying patients with ≥F2 fibrosis.
    METHODS: We applied the European (European Association for the Study of the Liver [EASL] 2012), Asian-Pacific (Asian-Pacific Association for the Study of the Liver [APASL] 2012), American (American Association for the Study of Liver Diseases [AASLD] 2009), and United States Panel Algorithm (USPA 2008) criteria to 366 consecutive hepatitis B e antigen-negative patients with liver biopsy samples: EASL, ALT >laboratory-defined upper limit of normal (ULN) and HBV DNA ≥2000 IU/mL (n = 171); APASL, ALT >2-fold laboratory-defined ULN and HBV DNA ≥2000 IU/mL (n = 87); AASLD, ALT >2-fold the updated ULN (0.5-fold ULN [corresponding to ≤19 U/L] for women and 0.75-fold the ULN [corresponding to ≤30 U/L] for men) and HBV DNA ≥20,000 IU/mL (n = 53); and USPA, ALT >updated ULN (>0.5-fold ULN for women and >0.75-fold ULN for men) and HBV DNA ≥2000 IU/mL (n = 173).
    RESULTS: Overall, 113 patients (30.9%) had ≥F2 fibrosis, which was more frequent among patients who fulfilled any guideline criteria (45.7% vs 17.9% for those who did not fulfill any criteria, P < .0001). In applying the EASL, AASLD, APASL, and USPA criteria, sensitivity and specificity values for detection of ≥F2 fibrosis were 45.6%, 58.5%, 56.3%, and 45.7% (P = .145) and 82.1%, 73.8%, 77.1%, and 82.4% (P = .366), respectively. The EASL criteria (area under the receiver operating characteristic [AUROC] curve, 0.66; 95% confidence interval [CI], 0.61-0.71) and USPA criteria (AUROC, 0.66; 95% CI, 0.58-0.73) performed better than APASL (AUROC, 0.64; 95% CI, 0.59-0.69; P = .421) and significantly better than the AASLD criteria (AUROC, 0.59; 95% CI, 0.54-0.64; P = .013).
    CONCLUSIONS: In hepatitis B e antigen-negative patients with chronic hepatitis, the EASL, AASLD, APASL, and USPA criteria identify patients with ≥F2 fibrosis with low levels of accuracy. However, the EASL and USPA criteria are the most accurate for identification of these patients.
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