To the Editor:
Tuberculosis (TB) remains the second leading cause of death from an infectious disease in adults. Extrapulmonary TB (EPTB) accounts for about 25% of all cases of active TB. Pleural TB is the second most common manifestation of EPTB.
Existing tests for the diagnosis of pleural TB have major limitations in terms of accuracy, time to diagnosis and drug resistance testing, and require special expertise for sample acquisition and interpretation of the results. Biopsy of the pleural tissue for combined histological examination and culture is considered the diagnostic gold standard, albeit imperfect [1,2]。
Xpert MTB / RIF Assay(Xpert; Cepheid,Sunnyvale,CA,USA)是一种快速,世界卫生组织(世卫组织)认可,可用于可以检测到两者的呼吸样本的自动化PCR测试Mycobacterium tuberculosis(MTB) and rifampicin resistance [3,4]。Given the limitations of available tests for the diagnosis of pleural TB, several studies have evaluated the performance of Xpert using pleural fluid as a sample type. Overall, these studies show limited accuracy with sensitivity averaging around 44% [5–7]。However, the preferred specimen for the diagnosis of pleural TB is pleural tissue. To date, the evaluation of Xpert performed on pleural tissue has been limited to isolated samples within larger studies [4,6,7]。
We enrolled consecutive adult patients that were evaluated for pleural TB in the pulmonary clinic and inpatient ward at the Christian Medical College, Vellore, India. Pleural TB was suspected based on clinical symptoms and radiographic evidence of a pleural effusion. Information on demographics, comorbidities, presenting symptoms and results of diagnostic evaluation were collected prospectively. The institutional review boards of the Christian Medical College and McGill University, Montreal, Canada, approved the study.
所有招募的患者都接受了胸腔饱和度,用于评估胸腔液。用常规诊断方法加工一种标本,包括荧光涂片显微镜,腺苷脱氨酶(Ada; deazyme Laboratories,San Diego,Ca,USA),液体培养物(分枝杆菌生长指标管; Becton Dickinson,Sparks,MD,美国)和固体培养物(Löwenstein-Jensen媒介)。第二个样品用于XPERT测试。在临床表明和安全可行时进行胸膜活检。用组织病理学,涂片显微镜和培养评价胸膜组织。
离心胸膜液(1370×g持续15分钟),浓缩沉积物,重悬于1ml原始上清液中,用于Xpert [5]。Pleural tissue was finely ground and re-suspended in 1 mL of sterile saline [8]。The Xpert “sample reagent” was added (2:1 ratio for both pleural fluid and pleural tissue samples) and, after incubation, 2 mL were transferred into a G4 cartridge.
We defined two composite reference standards (CRS) for the diagnosis of TB. The first CRS (CRS-1) identified confirmed TB if either acid-fast bacilli were identified on microscopic evaluation of pleural tissue or fluid, culture from pleural tissue or fluid was positive for MTB, histopathology of pleural tissue identified granulomas or MTB was identified in any other sample (e.g.sputum) from the same patient.
第二次CRS(CRS-2)包括以上所有内容,并且还包括患者,如果发现胸膜液是含有ADA水平的淋巴细胞渗出物> 40 u·l−1,在没有任何其他诊断的情况下解释胸腔积液。排除了胸膜Tb,如果任一组织病理学或细胞学是恶性肿瘤的诊断,或胸膜组织培养和组织病理学都没有表现出TB的证据,并且没有从任何其他样品中鉴定TB。
我们计算Xpert的敏感性和特异性,如使用两种参考标准对胸膜流体和胸膜组织进行的。分析和报告遵循报告诊断准确性的标准(Stard)[9]。
我们在2012年8月和2013年5月开始注册了96名患者。患者的中位数(末期)年龄为46(33-57)岁,20%是女性。除了两名患者患有TB的症状(i.e.fever, cough, weight loss, night sweats or shortness of breath). 29% of patients had an immunocompromising illness that would put them at higher risk for TB (diabetes, end-stage renal disease,etc.)和18%报告了活跃结核病的现有病史。
基于CRS-1,我们诊断出28例活跃的TB患者,其中八(29%)是组织培养证实。大多数(57%)诊断仅基于组织病理学。来自胸膜液的文化没有产生任何阳性结果(表格1). MTB was identified from another site (i.e.sputum or transbronchial biopsy) in three patients, suggesting that their pleural effusion was TB-related. Based on CRS-2, we diagnosed five additional cases of possible TB.
葡萄干Xpert在胸膜流体中检测到25例患者中的4例,如CRS-1所定义的确认结核病(在三个TB患者上进行的Xpert),导致敏感性为16.0%(95%CI 5-36%)。特异性为100%(66分,其中66分; 95%CI 95-100%)。使用CRS-2,XPERT敏感性为13.3%(含有30分的四个; 95%CI 4-31%)和特异性100%(61分,61分; 95%CI 94-100%)。胸膜血液Xpert检测到八种案例中的两种情况,阳性组织培养(表格1) and the one case that was pleural fluid smear positive (and also had an Xpert positive on a lymph node biopsy). Only one out of the four pleural fluid Xpert positive cases would have been detected based on biochemical findings (i.e.lymphocytic exudate with elevated ADA).
Xpert on pleural tissue in 55 patients was negative in all of the 14 confirmed TB cases as defined by CRS-1 (sensitivity 0%, 95% CI 0–23%). Three additional cases identified by CRS-2 were also Xpert negative. One false-positive result was obtained in a case with a histopathological diagnosis of malignancy, without any evidence of a concomitant TB infection (specificity 97.6%, 95% CI 87–100%) (表格1).
We observed no invalid results for Xpert testing of pleural fluid. In contrast, two invalid results were obtained when testing pleural tissue (one in a TB patient). For patients with positive Xpert result, the time to detection of TB was reduced to a few hours compared to 4 days on average for a diagnosis based on histopathology and 2–3 weeks for a diagnosis based on liquid culture.
据我们所知,这是迄今为止评估Xperurations使用胸膜组织进行胸膜TB的表现的最大研究。该研究突出了Xpert的灵敏度有限。在胸膜组织上进行的Xpert未检测到任何已识别的TB情况。当测试来自各个地点的组织时,Xpert的其他研究表明了良好的性能(e.g.淋巴结),这表明它可能是alternative to culture in tissue specimens [7]。Most of these studies have used only a culture reference standard [10]。然而,培养有限于其检测EPTB的能力,并且仅与文化证实的病例的比较可能会高估Xpert的敏感性。尽管如此,在我们的研究中,Xpert错过了组织上阳性培养的所有病例。
The low sensitivity in pleural fluid observed in this study has been described in previous studies [5–7,10]。Explanations for the limited sensitivity of Xpert in pleural fluid and tissue samples could relate to PCR inhibitors or insufficient sample volume in this paucibacillary disease. Further research on the optimisation of sample processing should be considered to enhance the sensitivity of the test [4]。In summary, our findings suggest that Xpert is of limited use in the diagnosis of pleural TB.
致谢
我们感激研究协调员(Deepa年代hankar, Shabana Gulam, Priya Samon and Amala Arumugam, all Department of Pulmonary Medicine, Christian Medical College, Vellore, India), and to the physicians of the Department of Pulmonary Medicine at the Christian Medical College for their support and contributions to this study.
脚注
Support statement: This work was supported by theCanadian Institutes of Health Research(grants MOP-89918) and a Grand Challenges Canada award (0026-01-04-01-01). M. Pai is supported by the European and Developing Countries Clinical Trials Partnership (EDCTP-TBNEAT grant) and the Fonds de recherche du Québec-Santé. C.M. Denkinger is supported by a Richard Tomlinson Fellowship at McGill University (Montreal, Canada) and a fellowship of the Burroughs–Wellcome Fund from theAmerican Society of Tropical Medicine and Hygiene.S.G. Schumacher is supported by the Quebec Respiratory Health Training Program. The funders had no role in the analysis of data and decision to publish.
利益冲突:披露可以在本文的在线版本旁边找到www.www.qdcxjkg.com
- ReceivedJune 18, 2013.
- Accepted2013年7月5日。
- ©ERS 2013