Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy.
Infectious and Tropical Diseases Unit, Florence Careggi University Hospital, Florence, Italy.
PLoS One. 2018 Jun 1;13(6):e0197825. doi: 10.1371/journal.pone.0197825. eCollection 2018.
Tuberculosis (TB) still is a major worldwide health problem, with 10.4 million new cases in 2016. Only 5-15% of people infected with M. tuberculosis develop TB disease while others remain latently infected (LTBI) during their lifetime. Thus, the absence of tests able to distinguish between latent infection and active tuberculosis is one of the major limits of currently available diagnostic tools.
A total of 215 patients were included in the study as active TB cases (n = 73), LTBI subjects (n = 88) and healthy persons (n = 54). Peripheral blood mononuclear cells (PBMCs) were isolated from each patient and the LIOSpot® TB anti-human IL-2 ELISpot assay was performed to test their proliferative response to M. tuberculosis antigens ESAT-6, CFP-10 and Ala-DH. Statistical analysis was performed to define the sensitivity and the specificity of the LIOSpot® TB kit for each antigen used and to set the best cut off value that enables discrimination between subjects with active TB or latent TB infection.
Comparing the LIOSpot® TB results for each tested antigen between uninfected and infected subjects and between people with latent infection and active TB disease, the differences were significant for each antigen (p< 0.0001) but the ROC analysis demonstrated a high accuracy for the Ala-DH test only, with a cut off value of 12.5 SFC per million PBMCs and the Ala-DH ROC curve conferred a 96% sensitivity and 100% specificity to the test. For the ESAT-6 antigen, with a best cut off value of 71.25 SFC per million PBMCs, a sensitivity of 86% and specificity of 36% was obtained. Finally, the best cut off value for CFP-10 was 231.25 SFC per million PBMCs, with a sensitivity of 80% and a specificity of 54%. Thus, as for IGRA assays such as Quantiferon and T-Spot TB tests, ESAT-6 and CFP-10 are unable to distinguish LTBI from active TB when IL-2 is measured. On the contrary, the IL-2 production induced by Ala-DH, measured by LIOSpot® TB kit, shows high sensitivity and specificity for active TB disease.
This study demonstrates that the LIOSpot® TB test is a highly useful diagnostic tool to discriminate between latent TB infection and active tuberculosis in adults patients.
结核病（TB）仍然是一个全球性的重大健康问题，2016 年有 1040 万例新发病例。在感染结核分枝杆菌的人中，只有 5-15%会发展为结核病，而其他人在其一生中则处于潜伏感染（LTBI）状态。因此，目前可用的诊断工具缺乏能够区分潜伏感染和活动性结核病的检测方法是一个主要限制因素。
共有 215 名患者被纳入研究，包括活动性结核病病例（n=73）、潜伏性结核感染受试者（n=88）和健康人（n=54）。从每位患者中分离外周血单核细胞（PBMCs），并进行 LIOSpot® TB 抗人 IL-2 ELISpot 检测，以测试其对结核分枝杆菌抗原 ESAT-6、CFP-10 和 Ala-DH 的增殖反应。进行统计分析以确定 LIOSpot® TB 试剂盒对每种使用的抗原的敏感性和特异性，并确定可区分活动性结核病或潜伏性结核病感染的最佳截止值。
将未感染者和感染者以及潜伏性感染和活动性结核病患者之间的 LIOSpot® TB 结果进行比较，对于每个测试抗原，差异均具有统计学意义（p<0.0001），但 ROC 分析仅显示 Ala-DH 检测具有较高的准确性，其最佳截止值为 12.5 SFC/百万 PBMCs，Ala-DH 的 ROC 曲线赋予该检测 96%的敏感性和 100%的特异性。对于 ESAT-6 抗原，最佳截止值为 71.25 SFC/百万 PBMCs，其敏感性为 86%，特异性为 36%。最后，CFP-10 的最佳截止值为 231.25 SFC/百万 PBMCs，其敏感性为 80%，特异性为 54%。因此，与 Quantiferon 和 T-Spot TB 等 IGRA 检测一样，当测量 IL-2 时，ESAT-6 和 CFP-10 无法区分 LTBI 与活动性 TB。相反，LIOSpot® TB 试剂盒测量的 Ala-DH 诱导的 IL-2 产生对活动性结核病具有很高的敏感性和特异性。
本研究表明，LIOSpot® TB 检测是一种非常有用的诊断工具，可用于区分成人潜伏性结核病感染和活动性结核病。
