Xpert Mtb/RIF全自动核酸扩增技术在结核病应急诊断中的应用

Use of the Xpert MTB/RIF Test for the urgent diagnosis tuberculosis

目的评价半巢式结核分枝杆菌/利福平全自动实时荧光定量核酸扩增技术(Xpert MTB/RIF)用于结核病应急诊断的临床价值。方法采集汕头市2015年1-12月疑似结核病突发公共卫生事件现场、口岸、急诊科、重症观察室的915例患者标本,应用涂片荧光染色法、BACTEC MGIT-960液体培养法、结核分枝杆菌DNA荧光定量法(TBDNA)、Xpert MTB/RIF技术分别进行检测,并将Xpert MTB/RIF利福平耐药结果与BACTEC MGIT-960药敏试验相比较。结果 915例患者中437例为活动性结核病患者,478例为非结核患者,Xpert MTB/RIF法的敏感性为51.72%(226/437),特异性为100%(478/478),Xpert MTB/RIF法的阳性检出率与涂片荧光染色法检测结果比较差异有统计学意义(χ~2=55.91,P<0.01),与BACTEC MGIT-960液体培养法、TB-DNA结果比较差异有统计学意义(χ2值分别为3.85和4.40,P<0.05);以BACTEC MGIT-960液体培养药敏试验为金标准,Xpert MTB/RIF检测利福平耐药的敏感度为92.31%(24/26),特异度为99.41%(168/169),二种方法具有良好的一致性(Kappa值为0.93)。结论 Xpert MTB/RIF法灵敏度和特异性高,操作简便、快速且易于开展,能在2h内报告结核分枝杆菌及利福平耐药结果,对结核病的应急诊断具有较高的应用价值。

Objective Xpert MTB/RIF is an automated semi-nested real-time quantitative nucleic acid amplification test to identify Mycobacterium tuberculosis and its resistance to rifampicin. The aim of this study was to evaluate the clinical value of Xpert MTB/RIF in the urgent diagnosis of tuberculosis. Methods Nine hundred and fifteen specimens were collected from sites of public health incidents presumably involving tuberculosis, from ports, and from patients in the e- mergency department and intensive care units in Shantou from January 2015 to December 2015. Each specimen was tested using fluorescence staining of smears, BACTEC MGIT-960 liquid culture, fluorometric quantification of M. tuberculosis DNA （TB-DNA）, and Xpert MTB/RIF. Resistance to rifampicin according to the Xpert MTB/RIF was compared to that according to a BACTEC MGIT-960 susceptibility test. Results Of 915 patients, 437 were diagnosed with active tuber- culosis and 478 were diagnosed as not having tuberculosis. Of the 437 patients diagnosed with active tuberculosis, 226 tested positive for M. tuberculosis according to Xpert MTB/RIF, for a rate of detection of 51.72%. One hundred and eighteen patients tested positive for M. tuberculosis according to fluorescence staining of smears, for a rate of detection of 27.00%. The rate of M. tuberculosis detection by the two methods differed significantly （χ^2 =55.91, P〈0.01）. One hundred and ninety-seven patients tested positive for M. tuberculosis according to the BACTEC MGIT-960 culture, for a rate of detection of 45.08%. The rate of M. tuberculosis detection by the BACTEC MGIT-960 culture and Xpert Mtb/ RFP differed significantly （X2=3.85, P〈0.05）. One hundred and ninety-five patients tested positive for M. tuberculosis according to TB-DNA, for a rate of detection of 44.62%. The rate of M. tuberculosis detection by TB-DNA and Xpert Mtb/RFP differed significantly （χ^2 = 4.40, P（0.05）. Four hundred and seventy-eight patients all tested negative for M. tuberculosis according to Xpert Mtb/RFP, but 10 tested positive for nontuberculous mycobacteria according to fluorescence staining of smears, 26 tested positive for nontuberculous mycobacteria according to the BACTEC MGIT-960 culture （including 10 that tested positive according to fluorescence staining of smears）, and 2 tested positive according to TBDNA. With clinical diagnosis serving as the gold standard, Xpert Mtb/RFP had a sensitivity of 51.72% （226/437）, a specificity of 100%（478/478）, a positive predictive value of 100% （226/226）, and a negative predictive value of 69.38%（478/689）. All 4 indices were higher than those of the other 3 methods. With the BACTEC MGIT-960 susceptibility test serving as the gold standard, Xpert MTB/RIF had a sensitivity of 92.31% （24/26） and a specificity of 99.41% （168/ 169） when determining resistance to rifampicin. Results of the two methods were in good agreement （Kappa=0.93）. Conclusion Xpert MTB/RIF has a high sensitivity and specificity, the procedure is simple, and the procedure can be quickly and easily performed. Xpert MTB/RIF can identify M. tuberculosis and report its rifampicin resistance in 2 h, which is of great value in the urgent diagnosis of tuberculosis.