Evaluation of a novel breath sensor for rapid, low-cost diagnosis of tuberculosis in children

项目总结 提高结核病(TB)的诊断水平对于减轻儿童结核病负担至关重要。关键挑战 包括许多儿童不产生痰，甚至在那些产生痰细菌负担中也是如此 通常都很低。因此，鉴定一种诊断结核病的高准确率的非痰检测方法。 儿童是一个关键的全球卫生优先事项。一种方法是评估挥发性有机化合物(VOC)在 呼气，这是很容易收集的所有年龄的儿童。最近的研究确定了至少两个 挥发性有机化合物--烟酸甲酯和对苯甲酸甲酯--结核分枝杆菌的副产品 因此，它应该存在于任何患有活动性结核病的人身上，无论年龄大小。这些VOC不会 似乎是由呼吸道的其他细菌排放的；在高浓度下似乎没有发现 在周围环境中；在结核病患者的呼气中被发现浓度很高，但 而不是健康对照组。然而，缺乏一种在护理点轻松测量特定VOCs的技术 一直是进一步验证和使用这些VOCs作为结核病诊断生物标记物的关键障碍。 这项建议的总体目标是确认呼气中的烟酸甲酯和对苯甲酸甲酯为 使用新型低成本手持设备检测用于诊断儿童胸腔内结核的生物标志物 设备。该装置是一种基于金属功能化的3D二氧化钛纳米管的固态传感器 施加特定电压梯度时绑定特定VOC的阵列。绑定会导致 与呼吸中存在的目标VOCs浓度成正比的电流。传感器已经被 定制专门结合烟酸甲酯和对苯甲酸甲酯，具有较低的检测下限。 此外，检测速度快(大约几分钟)，不需要试剂，不需要样品准备。 我们的中心假设是呼吸传感器将增加#年确诊结核病的比例 与目前推荐的分子检测方法(Xpert MTB/RIF，造父变种，美国)进行比较。 在目标1中，我们将通过以下方式将新型呼吸传感器进一步开发为可现场使用的儿童结核病诊断平台 1)在现有传感器中加入了正负向控制；2)设计了直接控制的样机。 收集呼气样本并将其传送到传感器(与收集呼吸袋中的呼气和 将袋子连接到传感器，如当前所做的)；以及3)执行可用性测试以改进设备 原型。在目标2中，我们将验证两个候选生物标志物和呼吸传感器设备的准确性 用于诊断儿童胸腔内结核。我们将招募和跟踪700-875名临床儿童 怀疑有结核病，四个对照组各有25名儿童。我们将评估诊断的准确性 呼吸传感器，参考NIH儿童结核病的病例定义，并纳入来自儿童的数据 对照组验证特异度并评估替代切点。完成这些目标将导致 一种新的呼吸技术用于儿童结核病非侵入性诊断的高质量数据。

PROJECT SUMMARY Improving diagnosis of tuberculosis (TB) is critical to reducing its burden among children. Key challenges include that many children do not produce sputum and, even among those who do, bacillary burden in sputum is often low. Therefore, identification of a non-sputum based test with high accuracy for diagnosing TB in children is a key global health priority. One approach is to evaluate volatile organic compounds (VOCs) in exhaled breath, which is easily collected from children of all ages. Recent research has identified at least two VOCs – methyl nicotinate and methyl p-anisate – that are a byproduct of Mycobacterium tuberculosis metabolism and should therefore be present in anyone with active TB, regardless of age. These VOCs do not appear to be emitted by other bacteria of the respiratory tract; do not appear to be found at high concentrations in the ambient environment; and have been identified at high concentrations in the breath of TB patients but not healthy controls. However, the lack of a technology to easily measure specific VOCs at the point-of-care has been a key barrier to further validation and use of these VOCs as a biomarker for TB diagnosis. The overall objective of this proposal is to validate methyl nicotinate and methyl p-anisate in exhaled breath as biomarkers for diagnosis of intra-thoracic TB in children when detected using a novel, low-cost, handheld device. The device is a solid-state sensor based on metal-functionalized 3D titanium dioxide (TiO2) nanotube arrays that bind specific VOCs when a specific voltage gradient is applied. Binding results in a change in current that is proportional to the concentration of target VOCs present in the breath. The sensor has been customized to specifically bind methyl-nicotinate and methyl p-anisate and has a low limit-of-detection. Furthermore, the detection is fast (on the order of minutes), reagent-free, and requires no sample preparation. Our central hypothesis is that the breath sensor will increase the proportion of confirmed TB diagnoses in children compared to the currently recommended molecular assay (Xpert MTB/RIF, Cepheid, USA). In Aim 1, we will further develop the novel breath sensor into a field-ready childhood TB diagnostic platform by 1) incorporating positive and negative controls into the existing sensor; 2) designing a prototype for direct collection and delivery of a breath sample to the sensor (versus collection of breath in a breath bag and connecting the bag to the sensor, as is currently done); and 3) performing usability testing to refine the device prototypes. In Aim 2, we will validate the accuracy of the two candidate biomarkers and breath sensor device for diagnosis of intra-thoracic TB in children. We will enroll and follow 700-875 children with a clinical suspicion of TB and 25 children in each of four control groups. We will assess diagnostic accuracy of the breath sensor in reference to NIH case definitions for pediatric TB and incorporate data from children in the control groups to verify specificity and evaluate alternate cut-points. Completion of these aims will result in high-quality data on the performance of a novel breath technology for non-invasive diagnosis of TB in children.