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中国防痨杂志 ›› 2019, Vol. 41 ›› Issue (2): 176-180.doi: 10.3969/j.issn.1000-6621.2019.02.010

所属专题: GeneXpert MTB/RIF检测技术相关研究

• 论著 • 上一篇    下一篇

GeneXpert MTB/RIF检测结核分枝杆菌对利福平耐药假阳性与标本低水平荷菌量的关系

刘元,周俊,崔晓利,雷佳媛,赵国连,党丽云()   

  1. 710100 西安市胸科医院
  • 收稿日期:2018-08-28 出版日期:2019-02-10 发布日期:2019-02-01
  • 通信作者: 党丽云 E-mail:dangliyun@sina.com
  • 基金资助:
    西安市卫生和计划生育委员会卫生科研人才培训项目(J201702021);西安市科技计划项目[2017120SF/YX014(3)]

The relationship between false-positive rifampicin resistant results of GeneXpert MTB/RIF and very low bacterial load in the clinical samples

Yuan LIU,Jun ZHOU,Xiao-li CUI,Jia-yuan LEI,Guo-lian ZHAO,Li-yun DANG()   

  1. Xi’an Chest Hospital, Xi’an 710100, China
  • Received:2018-08-28 Online:2019-02-10 Published:2019-02-01
  • Contact: Li-yun DANG E-mail:dangliyun@sina.com

摘要:

目的 对GeneXpert MTB/RIF检测(简称“GeneXpert检测”)结核分枝杆菌(MTB)及其对利福平耐药性的临床应用进行综合评价,并探讨GeneXpert检测MTB对利福平耐药假阳性与临床标本低水平荷菌量的关系。方法 收集2016年4月至2017年9月在西安市胸科医院就诊的2707例疑似肺结核患者的临床标本,其中痰标本1945例,肺泡灌洗液标本762例,同时进行GeneXpert检测、BACTEC MGIT 960液体培养(简称“MGIT 960法”)及药物敏感性试验(简称“药敏试验”),并将GeneXpert检测MTB对利福平耐药的标本进行GenoType MTBDRplus检测(简称“MTBDRplus检测”)。结果 GeneXpert检测临床标本的阳性率为39.8%(1077/2707),对利福平是否耐药不确定者有7例,荷菌量水平均为“极低”。以MGIT 960药敏试验结果为标准,GeneXpert检测MTB对利福平耐药的敏感度和特异度分别为89.4%(135/151)和94.7%(721/761)。两种检测方法判断MTB对利福平耐药不一致的结果共56例,其中GeneXpert检测MTB对利福平耐药而MGIT 960药敏试验检测为敏感的40例患者中,处于“极低”、“低”、“中等”和“高”4个菌量水平的患者分别为10例、6例、14例和10例。以MGIT 960药敏试验检测结果为标准,4个菌量级别中,GeneXpert检测MTB对利福平耐药的假阳性率分别为58.8%(10/17)、16.7%(6/36)、19.2%(14/73)和20.4%(10/49),差异有统计学意义(χ 2=13.981,P<0.05)。对40例患者进行MTBDRplus检测,结果显示,标本荷菌量水平为“低”、“中等”和“高”的30例标本均为对利福平耐药,与GeneXpert检测结果完全一致。标本荷菌量水平为“极低”的10例标本中,有2例MTBDRplus检测阴性,8例阳性;检测阳性的8例中有5例对利福平敏感,3例对利福平耐药。结论 GeneXpert技术检测MTB是否对利福平耐药具有较高的敏感度和特异度,但在检测样本荷菌量极低时,可能会出现假耐药的情况。

关键词: 分枝杆菌,结核, 利福平, 抗药性, 实验室技术和方法, 对比研究, 假阳性反应

Abstract:

Objective To assess the performance of GeneXpert MTB/RIF (GeneXpert) assay in the detection of Mycobacterium tuberculosis (MTB) and its rifampicin resistance, and further analyze the relationship between the false-positive rifampicin-resistant results of GeneXpert assay and the low bacterial load in the clinical samples. Methods From April 2016 to September 2017, a total of 2707 clinical samples (1945 sputum specimens and 762 alveolar lavage fluid specimens) of suspected pulmonary tuberculosis cases from Xi’an Chest Hospital were collected for GeneXpert detection, BACTEC MGIT 960 liquid culture and drug susceptibility test. Among them, GeneXpert detected rifampicin-resistant samples were further tested by GenoType MTBDRplus assay. Results The positive rate of GeneXpert assay in detecting MTB was 39.8% (1077/2707). Seven cases had “indeterminate” rifampicin resistance results and “Very low” bacterial load level. Considering MGIT 960 drug susceptibility test as the gold standard, the sensitivity and specificity of GeneXpert test in detecting rifampicin resistance was 89.4% (135/151) and 94.7% (721/761), respectively. The inconsistent results of two methods were found in 56 cases. Among them, 40 cases were rifampicin-resistant detected by GeneXpert but were rifampicin-sensitive detected by MGIT 960. Of the 40 patients, 10, 6, 14 and 10 showed a MTB load level of “Very low”, “Low”, “Medium” and “High”, respectively. Taking MGIT 960 test result as gold standard, the false-positive rates of rifampicin-resistance by GeneXpert in the four MTB load levels were 58.8% (10/17), 16.7% (6/36), 19.2% (14/73) and 20.4% (10/49), respectively; the difference was statistically significant (χ 2=13.981, P<0.05). Among the 40 cases, 30 cases with Low, Medium and High level of MTB load were rifampicin-resistant when detected by the MTBDRplus test, which was consistent with the GeneXpert results. As to the 10 cases with Very low level of MTB load, 2 cases were negative and 8 were positive by MTBDRplus test, and in the cases with positive results, 5 cases were rifampicin-sensitivity and 3 rifampicin-resistance. Conclusion The detection of MTB rifampicin-resistance with GeneXpert assay has a higher sensitivity and specificity. However, when the tested load of MTB is Very low, false drug resistant results may occur.

Key words: Mycobacterium tuberculosis, Rifampicin, Drug resistance, Laboratory techniques and procedures, Comparative study, False positive reactions