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Reassessment of the positive predictive value and specificity of Xpert MTB/RIF: a diagnostic accuracy study in the context of community-wide screening for tuberculosis.
Xpert MTB/RIF 的阳性预测值和特异性的重新评估: 一项在社区范围结核病筛查背景下的诊断准确性研究。

摘要

BACKGROUND:Community-wide screening for tuberculosis with Xpert MTB/RIF as a primary screening tool overcomes some of the limitations of conventional screening. However, concerns exist about the low positive predictive value of this test in screening settings. We did a cross-sectional assessment of this diagnostic test to directly estimate the actual positive predictive value of Xpert MTB/RIF when used in the setting of community-wide screening for tuberculosis, and to draw an inference about the specificity of the test for tuberculosis detection.
METHODS:Field staff visited households in 60 randomly selected villages in Ca Mau province, Vietnam. We included people aged 15 years or older who provided written informed consent and were able to produce 0·5 mL or more of sputum, irrespective of reported symptoms. Participants were tested with Xpert MTB/RIF, then those with positive results had two further sputum samples tested for smear microscopy and culture, and underwent chest radiography at the provincial TB Health Center. The positive predictive value of Xpert MTB/RIF was compared against two reference standards for tuberculosis diagnosis-a positive sputum culture for Mycobacterium tuberculosis, and a positive sputum culture or a chest radiograph consistent with active pulmonary tuberculosis. We then calculated the specificity of Xpert MTB/RIF for tuberculosis detection on the basis of these positive predictive values and disease prevalence in this setting.
FINDINGS:43 435 adults consented to screening with Xpert MTB/RIF. Sputum samples of 0·5 mL or greater were collected from 23 202 participants, producing 22 673 valid results. 169 participants had positive Xpert MTB/RIF results (0·39% of those screened and 0·75% of those with valid sputum results). The positive predictive value of Xpert MTB/RIF was 61·0% (95% CI 52·8-68·7) when compared against a positive sputum culture and 83·9% (76·8-89·2) when compared against a positive sputum culture or chest radiograph consistent with active tuberculosis. On the basis of these positive predictive values, the specificity of Xpert MTB/RIF was determined to be between 99·78% (95% CI 99·71-99·84) and 99·93% (99·88-99·96).
INTERPRETATION:The positive predictive value and specificity of Xpert MTB/RIF in the context of community-wide screening for tuberculosis is substantially higher than that predicted in previous studies. Our findings support the potential role of Xpert MTB/RIF as a primary screening tool to detect prevalent cases of tuberculosis in the community.
FUNDING:Australian National Health and Medical Research Council.

译文

背景: 以 Xpert MTB/RIF 为主要筛查工具的社区结核病筛查克服了传统筛查的一些局限性。然而,在筛选设置中存在对该测试的低阳性预测值的担忧。我们对这一诊断测试进行了横断面评估,以直接估计 Xpert MTB/RIF 在社区范围结核病筛查环境中的实际阳性预测值, 并推断出结核病检测的特异性。
方法: 实地工作人员走访了越南 Ca Mau 省随机选择的 60 个村庄。我们包括 15 岁或以上的人,他们提供书面知情同意书,并且能够产生 0 · 5ml 或更多的痰,而不考虑报告的症状。参与者接受了 Xpert MTB/RIF 测试,然后那些结果呈阳性的人又接受了两份痰样本的涂片显微镜和培养测试,并在省结核病保健中心接受了胸部 x光检查。将 Xpert MTB/RIF 的阳性预测值与结核分枝杆菌痰培养阳性的两种结核诊断参考标准进行比较, 痰培养阳性或胸片符合活动性肺结核。然后,我们根据这些阳性预测值和该环境下的疾病患病率,计算 Xpert MTB/RIF 对结核病检测的特异性。
结果: 43435 名成年人同意用 Xpert MTB/RIF 进行筛查。从 23 202 名参与者中收集了 0 · 5 mL 或以上的痰样本,产生了 22 673 个有效结果。169 名参与者的 Xpert MTB/RIF 结果呈阳性 (39% 的筛查结果和 75% 的有效痰结果)。Xpert MTB/RIF 的阳性预测值为 61 · 0% (95% CI 52 · 8-68 · 7) 当与痰培养阳性和 83 · 9% (76 · 8-89 · 2) 当与痰培养阳性或与活动性肺结核一致的胸片进行比较时。基于这些阳性预测值,Xpert MTB/RIF 的特异性被确定在 99 78% 之间 (95% CI 99 71-99 84) 和 93% (99 88-99 96)。
解释: Xpert MTB/RIF 在社区范围结核病筛查背景下的阳性预测值和特异性大大高于先前研究中的预测。我们的发现支持 Xpert MTB/RIF 作为检测社区结核病流行病例的主要筛查工具的潜在作用。
资金来源: 澳大利亚国家卫生和医学研究委员会。

positive predictive value

肿瘤 肿瘤基础研究 医疗诊断评价
概述  :  

positive predictive value是指阳性预测值,简写为PPV,是筛检试验检出的全部阳性例数中真正阳性症的比例,是一种反应试验结果阳性者患目标疾病的可能性。与阳性预测值相对应的是阴性预测值,这两者与灵敏度和特异性又有关。在进行一项诊断实验时判断是否患病时,结果分为四种:a,真阳性(实际有病,通过筛查试验确实判断为有病);b,假阳性(实际没病,但筛查试验判断为有病);c,真阴性(实际没病,筛查试验也判断为没病);d,假阴性(实际有病,筛查试验结果判断为没病)。阳性预测值=a/(

Positive   英 /ˈpɒzətɪv/   美 /'pɑzətɪv/

       adj. 积极的;[数] 正的,[医][化学] 阳性的;确定的,肯定的;实际的,真实的;绝对的;n. 正数;[摄] 正片

同根词   positively adv. 肯定地;明确地;断然地;posit n. 假设;设想;positivism n. 实证主义;实证论;积极性;武断;posit vt. 安置;假定

       Therefore, we should be positive toward life, so as to get happiness. 因此,我们应该积极的态度对待生活,从而得到幸福。

 

Predictive   英 /prɪ'dɪktɪv/   美 /prɪ'dɪktɪv/

       adj. 预言性的;成为前兆的

同根词   predictable adj. 可预言的;predictably adv. 可预言地;prediction n. 预报;预言;predictor n. [气象] 预报器;预言者;predict vi. 作出预言;作预料,作预报;predict vt. 预报,预言;预知

       To have predictive value, information need not be in the form of an explicit forecast. 资料要具有预测价值,不一定非要采取明确的预测形式。

 

Value   英 /'væljuː/   美 /'vælju/

       n. 值;价值;价格;重要性;确切涵义;vt. 评价;重视;估价

同根词   valuable adj. 有价值的;贵重的;可估价的;valued adj. 重要的;宝贵的;贵重的;经估价的;valueless adj. 无价值的;不值钱的;微不足道的;valuable n. 贵重物品;valuation n. 评价,估价;计算;valuate vt. 对…作估价

       Who pays for what value and when? 谁在什么时候为什么价值买单?

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