Department of Respiratory and Critical Care Medicine, Peking University People's Hospital, Beijing, People's Republic of China.
PLoS One. 2012;7(6):e38743. doi: 10.1371/journal.pone.0038743. Epub 2012 Jun 14.
Etiologic diagnoses of lower respiratory tract infections (LRTI) have been relying primarily on bacterial cultures that often fail to return useful results in time. Although DNA-based assays are more sensitive than bacterial cultures in detecting pathogens, the molecular results are often inconsistent and challenged by doubts on false positives, such as those due to system- and environment-derived contaminations. Here we report a nationwide cohort study on 2986 suspected LRTI patients across P. R. China. We compared the performance of a DNA-based assay qLAMP (quantitative Loop-mediated isothermal AMPlification) with that of standard bacterial cultures in detecting a panel of eight common respiratory bacterial pathogens from sputum samples. Our qLAMP assay detects the panel of pathogens in 1047(69.28%) patients from 1533 qualified patients at the end. We found that the bacterial titer quantified based on qLAMP is a predictor of probability that the bacterium in the sample can be detected in culture assay. The relatedness of the two assays fits a logistic regression curve. We used a piecewise linear function to define breakpoints where latent pathogen abruptly change its competitive relationship with others in the panel. These breakpoints, where pathogens start to propagate abnormally, are used as cutoffs to eliminate the influence of contaminations from normal flora. With help of the cutoffs derived from statistical analysis, we are able to identify causative pathogens in 750 (48.92%) patients from qualified patients. In conclusion, qLAMP is a reliable method in quantifying bacterial titer. Despite the fact that there are always latent bacteria contaminated in sputum samples, we can identify causative pathogens based on cutoffs derived from statistical analysis of competitive relationship.
ClinicalTrials.gov NCT00567827.
下呼吸道感染（LRTI）的病因诊断主要依赖于细菌培养，而细菌培养往往不能及时提供有用的结果。虽然基于 DNA 的检测比细菌培养更能检测病原体，但分子结果往往不一致，并且存在假阳性的疑虑，例如由于系统和环境来源的污染而导致的假阳性。在这里，我们报告了一项针对中国 2986 例疑似 LRTI 患者的全国性队列研究。我们比较了一种基于 DNA 的检测 qLAMP（定量环介导等温扩增）与标准细菌培养在检测痰样本中八种常见呼吸道细菌病原体的性能。我们的 qLAMP 检测方法在 1533 名合格患者中的 1047 名（69.28%）患者中检测到了该病原体组。我们发现，qLAMP 定量检测到的细菌滴度是样本中细菌在培养检测中可被检测到的概率的预测指标。两种检测方法的相关性符合逻辑回归曲线。我们使用分段线性函数来定义潜在病原体与该病原体组中其他病原体的竞争关系突然改变的断点。这些病原体开始异常繁殖的断点被用作截断值，以消除正常菌群污染的影响。通过使用统计分析得出的截断值，我们能够从合格患者中识别出 750 名（48.92%）患者的病原体。总之，qLAMP 是一种定量细菌滴度的可靠方法。尽管痰样本中总是存在潜伏的细菌污染，但我们可以根据竞争关系的统计分析得出的截断值来识别病原体。
ClinicalTrials.gov NCT00567827。
