Lange B, Khan P, Kalmambetova G, Al-Darraji H A, Alland D, Antonenka U, Brown T, Balcells M E, Blakemore R, Denkinger C M, Dheda K, Hoffmann H, Kadyrov A, Lemaitre N, Miller M B, Nikolayevskyy V, Ntinginya E N, Ozkutuk N, Palacios J J, Popowitch E B, Porcel J M, Teo J, Theron G, Kranzer K
Centre for Chronic Immunodeficiency, Division of Infectious Diseases, Department of Internal Medicine II, Faculty of Medicine, Medical Center-University of Freiburg, Freiburg, Germany.
London School of Hygiene & Tropical Medicine, London, UK.
Int J Tuberc Lung Dis. 2017 May 1;21(5):493-502. doi: 10.5588/ijtld.16.0702.
Xpert® MTB/RIF is the most widely used molecular assay for rapid diagnosis of tuberculosis (TB). The number of polymerase chain reaction cycles after which detectable product is generated (cycle threshold value, CT) correlates with the bacillary burden.OBJECTIVE To investigate the association between Xpert CT values and smear status through a systematic review and individual-level data meta-analysis.
Studies on the association between CT values and smear status were included in a descriptive systematic review. Authors of studies including smear, culture and Xpert results were asked for individual-level data, and receiver operating characteristic curves were calculated.
Of 918 citations, 10 were included in the descriptive systematic review. Fifteen data sets from studies potentially relevant for individual-level data meta-analysis provided individual-level data (7511 samples from 4447 patients); 1212 patients had positive Xpert results for at least one respiratory sample (1859 samples overall). ROC analysis revealed an area under the curve (AUC) of 0.85 (95%CI 0.82-0.87). Cut-off CT values of 27.7 and 31.8 yielded sensitivities of 85% (95%CI 83-87) and 95% (95%CI 94-96) and specificities of 67% (95%CI 66-77) and 35% (95%CI 30-41) for smear-positive samples.
Xpert CT values and smear status were strongly associated. However, diagnostic accuracy at set cut-off CT values of 27.7 or 31.8 would not replace smear microscopy. How CT values compare with smear microscopy in predicting infectiousness remains to be seen.
Xpert® MTB/RIF是用于快速诊断结核病（TB）的应用最为广泛的分子检测方法。产生可检测产物后的聚合酶链反应循环数（循环阈值，CT）与细菌负荷相关。目的通过系统评价和个体水平数据的荟萃分析，研究Xpert CT值与涂片结果之间的关联。
关于CT值与涂片结果之间关联的研究纳入描述性系统评价。要求纳入涂片、培养及Xpert结果的研究作者提供个体水平数据，并计算受试者工作特征曲线。
在918篇文献中，10篇纳入描述性系统评价。来自可能与个体水平数据荟萃分析相关研究的15个数据集提供了个体水平数据（来自4447例患者的7511份样本）；1212例患者至少一份呼吸道样本的Xpert结果为阳性（共1859份样本）。ROC分析显示曲线下面积（AUC）为0.85（95%CI 0.82 - 0.87）。对于涂片阳性样本，CT值截断点为27.7和31.8时，敏感性分别为85%（95%CI 83 - 87）和95%（95%CI 94 - 96），特异性分别为67%（95%CI 66 - 77）和35%（95%CI 30 - 41）。
Xpert CT值与涂片结果密切相关。然而，CT值截断点设定为27.7或31.8时的诊断准确性并不能替代涂片镜检。CT值在预测传染性方面与涂片镜检相比如何仍有待观察。
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