Londono-Avendano María Aurora, Libreros Gerardo, Osorio Lyda, Parra Beatriz
Departamento de Microbiología, Escuela de Ciencias Básicas, Facultad de Salud, Universidad del Valle, Calle 4B # 36-00, edificio 120, oficina 223/229, Cali 760043, Colombia.
Escuela de Salud Pública, Facultad de Salud, Universidad del Valle, Calle 4B # 36-00, edificio 120, oficina 223/229, Cali 760043, Colombia.
Diagnostics (Basel). 2022 Mar 29;12(4):848. doi: 10.3390/diagnostics12040848.
Loop-mediated amplification has been promoted for SARS-CoV-2 screening, however, antigen tests are preferred in low-income countries and remote zones. Poor training in molecular biology, plus the need for RNA purification or reading instruments to overcome issues of sensitivity in colorimetric detection, are some of the reasons limiting the use of this technique. In this study, nasopharyngeal swabs, aspirates and saliva were amplified in an in-house LAMP assay and subject to colorimetric detection, achieved by the naked eye and by image analysis with a mobile application. Accuracy of detection by the naked eye ranged from 61-74% but improved to 75-86% when using the application. Sensitivity of the digital approach was 81% and specificity 83%, with poor positive predictive value, and acceptable negative predictive value. Additionally to the reported effect of some transport media's pH, the presence of mucus and warming up of reagents while setting up the reaction critically affected performance. Accuracy per type of sample was 55, 70 and 80%, for swabs, aspirates and saliva, respectively, suggesting potential to improve the test in saliva. This assay, carried out in a closed tube, reduces contamination, has few pipetting steps and requires minimal equipment. Strategies to improve performance and implications of the use this sort of colorimetric LAMP for massive testing are discussed.
环介导等温扩增技术已被推广用于新型冠状病毒2（SARS-CoV-2）筛查，然而，在低收入国家和偏远地区，抗原检测更受青睐。分子生物学方面培训不足，以及需要进行RNA纯化或使用读取仪器来克服比色检测中的灵敏度问题，是限制该技术应用的部分原因。在本研究中，采用内部环介导等温扩增（LAMP）检测法对鼻咽拭子、抽吸物和唾液进行扩增，并通过肉眼和使用移动应用程序进行图像分析来进行比色检测。肉眼检测的准确率在61%-74%之间，但使用该应用程序时准确率提高到75%-86%。数字检测方法的灵敏度为81%，特异性为83%，阳性预测值较低，阴性预测值可接受。除了报道的某些运输介质pH值的影响外，样本中存在黏液以及在设置反应时试剂升温对检测性能有严重影响。拭子、抽吸物和唾液样本的准确率分别为55%、70%和80%，这表明唾液检测有改进的潜力。该检测在封闭管中进行，可减少污染，移液步骤少，所需设备最少。文中讨论了提高检测性能的策略以及使用这种比色LAMP进行大规模检测的意义。
