Department of Epidemiology and Preclinical Research, L. Spallanzani National Institute for Infectious Diseases, IRCCS, Rome, Italy.
BMC Infect Dis. 2009 Nov 21;9:182. doi: 10.1186/1471-2334-9-182.
Interferon-gamma (IFN-gamma) release assays (IGRAs) were designed to detect latent tuberculosis infection (LTBI). However, discrepancies were found between the tuberculin skin test (TST) and IGRAs results that cannot be attributed to prior Bacille Calmètte Guerin vaccinations. The aim of this study was to evaluate tools for improving LTBI diagnosis by analyzing the IFN-gamma response to RD1 proteins in prolonged (long-term response) whole blood tests in those subjects resulting negative to assays such as QuantiFERON-TB Gold In tube (QFT-IT).
The study population included 106 healthy TST+ individuals with suspected LTBI (recent contact of smear-positive TB and homeless) consecutively enrolled. As controls, 13 healthy subjects unexposed to M. tuberculosis (TST-, QFT-IT-) and 29 subjects with cured pulmonary TB were enrolled. IFN-gamma whole blood response to RD1 proteins and QFT-IT were evaluated at day 1 post-culture. A prolonged test evaluating long-term IFN-gamma response (7-day) to RD1 proteins in diluted whole blood was performed.
Among the enrolled TST+ subjects with suspected LTBI, 70/106 (66.0%) responded to QFT-IT and 64/106 (60.3%) to RD1 proteins at day 1. To evaluate whether a prolonged test could improve the detection of LTBI, we set up the test using cured TB patients (with a microbiologically diagnosed past pulmonary disease) who resulted QFT-IT-negative and healthy controls as comparator groups. Using this assay, a statistically significant difference was found between IFN-gamma levels in cured TB patients compared to healthy controls (p < 0.006). Based on these data, we constructed a receiver operating characteristic (ROC) curve and we calculated a cut-off. Based on the cut-off value, we found that among the 36 enrolled TST+ subjects with suspected LTBI not responding to QFT-IT, a long term response to RD1 proteins was detected in 11 subjects (30.6%).
These results indicate that IFN-gamma long-term response to M. tuberculosis RD1 antigens may be used to detect past infection with M. tuberculosis and may help to identify additional individuals with LTBI who resulted negative in the short-term tests. These data may provide useful information for improving immunodiagnostic tests for tuberculosis infection, especially in individuals at high risk for active TB.
干扰素-γ（IFN-γ）释放检测（IGRAs）旨在检测潜伏性结核感染（LTBI）。然而，结核菌素皮肤试验（TST）和 IGRAs 结果之间存在差异，这些差异不能归因于卡介苗疫苗接种。本研究旨在通过分析 RD1 蛋白在 TST+疑似 LTBI（近期与涂阳肺结核接触和无家可归者）人群中延长（长期反应）全血检测中的 IFN-γ反应，评估改善 LTBI 诊断的工具。
研究人群包括 106 例连续入组的 TST+疑似 LTBI 健康个体（近期与涂阳肺结核接触和无家可归者）。作为对照，纳入 13 例未接触过结核分枝杆菌（TST-、QFT-IT-）的健康受试者和 29 例治愈的肺结核患者。在培养后第 1 天，评估 RD1 蛋白和 QFT-IT 对全血 IFN-γ的反应。进行了一项延长的试验，以评估 RD1 蛋白在稀释全血中的长期 IFN-γ反应（7 天）。
在 106 例 TST+疑似 LTBI 受试者中，70/106（66.0%）对 QFT-IT 有反应，64/106（60.3%）对 RD1 蛋白有反应。为了评估延长试验是否可以提高 LTBI 的检测率，我们将已治愈的肺结核患者（经微生物学诊断为既往肺部疾病）和健康对照作为比较组，使用该试验。与健康对照组相比，治愈的肺结核患者的 IFN-γ水平存在统计学显著差异（p<0.006）。基于这些数据，我们构建了受试者工作特征（ROC）曲线并计算了临界值。基于临界值，我们发现在 36 例未对 QFT-IT 有反应的 TST+疑似 LTBI 受试者中，11 例（30.6%）检测到对 RD1 蛋白的长期反应。
这些结果表明，结核分枝杆菌 RD1 抗原的 IFN-γ长期反应可用于检测过去的结核分枝杆菌感染，并可能有助于识别在短期检测中呈阴性的 LTBI 个体。这些数据可能为改善结核感染的免疫诊断检测提供有用信息，尤其是在活动性结核病高危人群中。
