Point of care diagnosis of gastrointestinal disease using laser spectroscopy

医学诊断正从实验室走向床边。复杂的实验室分析有一种强烈的趋势，即由几乎没有或没有受过专业培训的人员在护理点进行的测试来补充，甚至取代。快速检测的一个重要特点是其结果的时间短。实时或接近实时地提供诊断信息通过实现快速和有针对性的干预来支持临床决策，从而改善患者的预后并促进有限医疗资源的有效利用。为此，开发能够快速准确测量疾病化学指标（生物标志物）的新型仪器是一个战略优先事项。艰难梭菌感染（CDI）是一个未满足的临床诊断需求的例子，也是本研究的主要焦点。CDI是一种医院获得性感染，可引起灾难性腹泻，延长住院时间，并可对脆弱个体造成致命影响。它是高度传染性的-目前英国国民保健服务干预政策要求，不明原因腹泻的患者必须被隔离和治疗的疾病之前，积极的诊断是可用的。目前的CDI检测使用传统的实验室“湿化学”酶和核酸检测，诊断性能有限，交货时间以小时计。误诊可能导致患者被不必要地隔离出病房或接受不必要的抗生素治疗，从而导致抗生素耐药性的发展。从一系列人体样本（如呼吸、血液、尿液）中释放的挥发性有机化合物（VOC）水平的变化已知与代谢状态相关，并与特定疾病有关。胃肠道提供了特别丰富的信息来源，因为许多疾病状态与肠道细菌种群（微生物组）的变化有关，导致产生的VOC发生变化，这可以使用光谱法进行测量。我们的愿景是开发一种基于气相中这些挥发性生物标志物的光学测量的新方法。通过测量患者粪便样本产生的特定生物标志物化学物质的水平，我们的目标是提供胃病发展的早期预警。这种方法的重要好处是：-使用标准临床程序采集粪便样本，这是今天症状出现时的正常做法。挥发性标记物可使用激光光谱法测量，获得结果的时间较短（1-2分钟）。该测量对单个VOC具有高度选择性，重要的是可以根据300多种物种的复杂背景矩阵识别生物标志物。该方法需要最少的样品制备，避免使用试剂，并使其适用于即时诊断。由于测量系统不与样品物理接触，因此传感器不会受到干扰或污染。它在临床上是非侵入性的，因此适合在疾病监测中重复使用，不像结肠镜和乙状结肠镜等技术广泛用于慢性疾病诊断，但不能每天使用。该方法将允许活动性疾病与仅仅携带艰难梭菌（后者在英国人口中占很大比例，没有不良影响）区分开来。我们将开发一个灵活的诊断平台，以诊断CDI为目标。肠道微生物组的紊乱也与一系列其他胃肠道疾病有关，包括炎症性肠病和结直肠癌，以及其他疾病，如糖尿病。因此，该技术具有广泛的潜在应用，用于医疗诊断和监测一系列疾病的护理点。

Medical diagnostics is moving from laboratory to bedside. There is a strong trend for complex laboratory analyses to be supplemented, or even replaced, by tests that can be performed at the point-of-care (PoC) by personnel with little or no specialist training. An important feature of PoC tests is their short time-to-result. Provision of diagnostic information at or near real-time supports clinical decisionmaking by enabling rapid and targeted intervention, which improves patient outcome and promotes efficient use of limited healthcare resources. To this end, development of novel instrumentation capable of rapid and accurate measurement of chemical indicators of disease (biomarkers) is a strategic priority.Clostridium difficile infection (CDI) is an example of an unmet clinical need for PoC diagnostics and is the main focus of this study. CDI is a hospital-acquired infection which produces catastrophic diarrhoea, prolongs hospital stays and can prove fatal in vulnerable individuals. It is highly contagious - current UK NHS intervention policy requires that patients with unexplained diarrhoea must be isolated and treated for the disease before a positive diagnosis is available. Current tests for CDI use traditional laboratory "wet chemistry" enzymatic and nucleic acid assays, with limited diagnostic performance and a lead time measured in hours. Misdiagnosis can lead to patients being unnecessarily isolated from wards or treated unnecessarily with antibiotics, which contributes to the development of antimicrobial resistance.Variation in the levels of volatile organic compounds (VOCs) emitted from a range of human samples (e.g. breath, blood, urine) are known to be associated with metabolic status and have been linked to particular diseases. The gastrointestinal tract offers a particularly rich source of information, since many disease states are associated with changes in the bacterial population of the gut (the microbiome) resulting in changes to the VOCs produced, which can be measured using optical spectroscopy. Our vision is to develop a novel approach based on optical measurement of these volatile biomarkers in the gas phase. By measuring the level of specific biomarker chemicals produced by samples of patients' faeces, we aim to provide early warning of the development of gastric disease. Important benefits of this approach are:- Samples of faeces are taken using standard clinical procedures, as is normal practice today when symptoms develop.- Volatile markers may be measured using laser spectroscopy, with a short time-to-result (1-2 minutes). The measurement is highly selective to individual VOCs, which importantly will allow identification of biomarkers against a complex background matrix of over 300 species.- The method requires minimal sample preparation, avoiding the use of reagents and making it suitable for point-of-care diagnosis.- Because the measurement system is not in physical contact with the sample, there is no interference or fouling of the sensor.- It is clinically non-invasive, so is suitable for repeated use in disease monitoring, unlike techniques such as colonoscopy and sigmoidoscopy which are widely used in chronic disease diagnosis but cannot be used on a daily basis.- The method will allow active disease to be distinguished from mere carriage of Clostridium difficile (the latter being present in a significant percentage of the UK population without ill effect).We will develop a flexible diagnostic platform targeted at diagnosis of CDI. Disturbances in the gut microbiome are also associated with a range of other gastrointestinal conditions including inflammatory bowel disease and colorectal cancer, and with other diseases such as diabetes. This technique therefore has wide potential application for medical diagnosis and monitoring of a range of diseases at point of care.