University of Leicester, Department of Respiratory Sciences, LE1 7RH Leicester, United Kingdom.
University of Leicester, Department of Chemistry, LE1 7RH Leicester, United Kingdom.
J Breath Res. 2021 Jan 11;15(2). doi: 10.1088/1752-7163/abcd2a.
The headspace of a biological sample contains exogenous volatile organic compounds (VOCs) present within the sampling environment which represent the background signal. This study aimed to characterise the background signal generated from a headspace sampling system in a clinical site, to evaluate intra- and inter-day variation of background VOC and to understand the impact of a sample itself upon commonly reported background VOC using sputum headspace samples from severe asthmatics. The headspace, in absence of a biological sample, was collected hourly from 11am to 3pm within a day (time of clinical samples acquisition), and from Monday to Friday in a week, and analysed by thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS). Chemometric analysis identified 1120 features, 37 of which were present in at least the 80% of all the samples. The analyses of intra- and inter-day background variations were performed on 13 of the most abundant features, ubiquitously present in headspace samples. The concentration ratios relative to background were reported for the selected abundant VOC in 36 asthmatic sputum samples, acquired from 36 stable severe asthma patients recruited at Glenfield Hospital, Leicester, UK. The results identified no significant intra- or inter-day variations in compounds levels and no systematic bias of-scores, with the exclusion of benzothiazole, whose abundance increased linearly between 11am and 3pm with a maximal intra-day fold change of 2.13. Many of the identified background features are reported in literature as components of headspace of biological samples and are considered potential biomarkers for several diseases. The selected background features were identified in headspace of all severe asthma sputum samples, albeit with varying levels of enrichment relative to background. Our observations support the need to consider the background signal derived from the headspace sampling system when developing and validating headspace biomarker signatures using clinical samples.
生物样本的顶空部分包含存在于采样环境中的外源性挥发性有机化合物（VOC），这些化合物代表背景信号。本研究旨在对临床环境中顶空采样系统产生的背景信号进行特征描述，评估背景 VOC 的日内和日间变化，并通过来自严重哮喘患者的痰液顶空样本，了解样品本身对常用背景 VOC 的影响。在一天中（临床样本采集时间），从上午 11 点到下午 3 点，在没有生物样本的情况下，每隔一小时从临床样本采集地点采集一次顶空部分，并在一周内从周一到周五进行采集，然后通过热解吸-气相色谱-质谱联用（TD-GC-MS）进行分析。化学计量学分析确定了 1120 个特征，其中 37 个特征至少存在于所有样本的 80%中。对 13 个最丰富特征的日内和日间背景变化进行了分析，这些特征普遍存在于顶空样本中。在所选择的 36 例稳定严重哮喘患者的 36 例哮喘痰液样本中，报告了相对背景的选定丰富 VOC 的浓度比，这些患者均来自英国莱斯特的格伦菲尔德医院。结果表明，化合物水平没有明显的日内或日间变化，也没有系统偏差的分数，除了苯并噻唑，其丰度在上午 11 点至下午 3 点之间呈线性增加，日内最大倍数变化为 2.13。许多已识别的背景特征在文献中被报道为生物样本顶空部分的组成部分，被认为是几种疾病的潜在生物标志物。在所选择的背景特征在所有严重哮喘痰液样本的顶空中均有发现，尽管相对于背景的富集程度不同。我们的观察结果支持在使用临床样本开发和验证顶空生物标志物特征时，需要考虑顶空采样系统产生的背景信号。
