Masood Kiran Iqbal, Jamil Bushra, Akber Alnoor, Hassan Maheen, Islam Muniba, Hasan Zahra
1Department of Pathology and Laboratory Medicine, The Aga Khan University, Stadium Road, P.O.Box 3500, Karachi, Pakistan.
2Department of Medicine, The Aga Khan University, Karachi, Pakistan.
Trop Dis Travel Med Vaccines. 2020 Feb 19;6:3. doi: 10.1186/s40794-020-0102-z. eCollection 2020.
There were 10 million new cases of tuberculosis (TB) in 2017. To eliminate TB, it is necessary to diagnose active TB and latent tuberculosis infection (LTBI). Diagnosis of paucibacillary disease and in extrapulmonary TB (EPTB) remains challenging; low mycobacterial load can be missed by microbiological or molecular based confirmation; EPTB, can be misdiagnosed due to absence of site specific specimens for testing. Interferon gamma release assays (IGRA) use T cell-based Interferon-gamma (IFN-γ) to identify infection with (MTB) but cannot discriminate between active and LTBI. We investigated how IGRA was being used in a high burden low resource setting.
We conducted a retrospective review of 149 consecutive cases received for QuantiFERON-TB Gold In-Tube Assay (QFT-GIT) testing in routine clinical service.
Fifty-six cases were QFT-GIT positive and 93 were QFT-GIT negative. Thirty-six per cent of QFT-GIT tested cases had active TB. Of QFT-GIT positive cases, 59% patients had active TB; 10 with pulmonary and 23 with extra-pulmonary TB. The remaining 41% QFT-positive cases were LTBI. Of the QFT-GIT negative cases, 22% had active TB. Co-morbid conditions were present in 37% of QFT-GIT positive and 60% of QFT-GIT negative cases.
Our study shows that IGRA is being used as an adjunct test for active TB in this population. It highlights the complexity of interpreting QFT-GIT results particularly for QFT-GIT negative cases when ruling out MTB infection.
2017年有1000万例新发结核病病例。为了消除结核病，有必要诊断活动性结核病和潜伏性结核感染（LTBI）。诊断菌量少的疾病和肺外结核病（EPTB）仍然具有挑战性；基于微生物学或分子学的确诊方法可能会遗漏低分枝杆菌载量的情况；由于缺乏用于检测的特定部位标本，EPTB可能会被误诊。干扰素γ释放试验（IGRA）利用基于T细胞的干扰素γ（IFN-γ）来识别结核分枝杆菌（MTB）感染，但无法区分活动性感染和LTBI。我们调查了在高负担、低资源环境中IGRA的使用情况。
我们对在常规临床服务中接受结核感染T细胞检测（QFT-GIT）的149例连续病例进行了回顾性研究。
56例QFT-GIT检测呈阳性，93例呈阴性。接受QFT-GIT检测的病例中有36%患有活动性结核病。在QFT-GIT检测呈阳性的病例中，59%的患者患有活动性结核病；10例为肺结核，23例为肺外结核。其余41%的QFT检测阳性病例为LTBI。在QFT-GIT检测呈阴性的病例中，22%患有活动性结核病。37%的QFT-GIT检测阳性病例和60%的QFT-GIT检测阴性病例存在合并症。
我们的研究表明，在这一人群中，IGRA被用作活动性结核病的辅助检测方法。它凸显了解释QFT-GIT结果的复杂性，尤其是在排除MTB感染时对于QFT-GIT检测阴性病例的解释。
