Polepole Pascal, Kabwe Mwila, Kasonde Mpanga, Tembo John, Shibemba Aaron, O'Grady Justin, Kapata Nathan, Zumla Alimuddin, Bates Matthew
Department of Biomedical Sciences, University of School of Medicine, Lusaka, Zambia.
University of and University College London Medical School (UNZA-UCLMS) Research and Training Programme, University Teaching Hospital, Lusaka, Zambia.
Int J Mycobacteriol. 2017 Jan-Mar;6(1):87-93. doi: 10.4103/2212-5531.201892.
OBJECTIVE/BACKGROUND: Extrapulmonary tuberculosis (EPTB), which accounts for 10%-40% of the global burden of TB, with the highest incidence in Sub-Saharan Africa, is strongly associated with human immunodeficiency virus infection. Diagnosing EPTB is challenging, and recently, there has been a concerted effort to evaluate the latest molecular diagnostics for diagnosing TB in a range of specimen types. The Xpert MTB/RIF assay (Cepheid, Sunnyvale, CA, USA) is one such technology, which simultaneously detects Mycobacterium tuberculosis and rifampicin resistance. Our objective was to evaluate the accuracy of the Xpert MTB/RIF assay for the diagnosis of EPTB and detection of rifampicin resistance in routinely processed formalin-fixed, paraffin-embedded (FFPE) tissues, compared with histological detection of TB as the gold standard.
A convenience set of 100 biobanked FFPE tissues, including lymph nodes (n = 64), male genital tract tissue (n = 10), abdominal tissue (n = 8), female genital tissue (n = 5), breast tissue (n = 5), synovial tissue (n = 4), skin (n = 2), tongue tissue (n = 1), and thyroid (n = 1), from routine cases of clinically suspected EPTB admitted to the University Teaching Hospital, Lusaka, Zambia, were analyzed using the Xpert MTB/RIF assay and in-house polymerase chain reaction (PCR) assay targeting IS6110, in parallel with Ziehl-Neelsen (ZN) staining, against histology as the gold standard.
Some 66% of specimens had histological evidence of TB infection. ZN staining was positive for TB in 8% of cases, and Xpert MTB/RIF was positive for TB in 25% of cases. Taking histology as the gold standard, the sensitivity and specificity were as follows: In lymph tissue the accuracy of the Xpert MTB/RIF assay was 41% (95%CI 27-57), not significantly better than ZN or the in-house PCR assay. In non-lymph tissue the sensitivity of the in-house PCR assay was 82% (95%CI: 56%-95%), significantly higher than the Xpert MTB/RIF assay (P = 0.004). The Xpert MTB/RIF assay indicated rifampicin resistance in just three cases.
The Xpert MTB/RIF assay is potentially a useful tool for the diagnosis of TB in routine FFPE tissues.
目的/背景：肺外结核病（EPTB）占全球结核病负担的10%-40%，在撒哈拉以南非洲发病率最高，与人类免疫缺陷病毒感染密切相关。EPTB的诊断具有挑战性，最近，人们齐心协力评估了一系列标本类型中用于诊断结核病的最新分子诊断方法。Xpert MTB/RIF检测（美国加利福尼亚州桑尼维尔市赛沛公司）就是这样一种技术，它能同时检测结核分枝杆菌和利福平耐药性。我们的目的是与作为金标准的结核病组织学检测相比，评估Xpert MTB/RIF检测在常规处理的福尔马林固定石蜡包埋（FFPE）组织中诊断EPTB和检测利福平耐药性的准确性。
选取赞比亚卢萨卡大学教学医院临床怀疑为EPTB的常规病例中100份生物样本库的FFPE组织，包括淋巴结（n = 64）、男性生殖道组织（n = 10）、腹部组织（n = 8）、女性生殖组织（n = 5）、乳腺组织（n = 5）、滑膜组织（n = 4）、皮肤（n = 2）、舌组织（n = 1）和甲状腺（n = 1），使用Xpert MTB/RIF检测和针对IS6110的内部聚合酶链反应（PCR）检测进行分析，并与齐-尼氏（ZN）染色同时进行，以组织学作为金标准。
约66%的标本有结核病感染的组织学证据。ZN染色8%的病例呈结核病阳性，Xpert MTB/RIF检测25%的病例呈结核病阳性。以组织学作为金标准，敏感性和特异性如下：在淋巴组织中，Xpert MTB/RIF检测的准确性为41%（95%CI 27-57），并不显著优于ZN或内部PCR检测。在非淋巴组织中，内部PCR检测的敏感性为82%（95%CI：56%-95%），显著高于Xpert MTB/RIF检测（P = 0.004）。Xpert MTB/RIF检测仅在3例中显示有利福平耐药性。
Xpert MTB/RIF检测可能是常规FFPE组织中结核病诊断的有用工具。
