Analysis Of The Value Of Xpert MTB/RIF Assay Using Bronchoalveolar Lavage Fluid In The Clinical Diagnosis Of Pulmonary Tuberculosis

Objective:To explore the value of Xpert MTB/RIF assay using bronchoalveolar lavage fluid in the clinical diagnosis of pulmonary tuberculosis and the accuracy of Xpert MTB/RIF technique in rifampicin resistance test.Methods:A retrospective analysis of 167 cases of suspected pulmonary tuberculosis in the fourth tuberculosis area of Chengdu Public Health Clinical Medical Center from June2017 to May 2018 was made.All patients were sent for acid-fast staining smear,BACTEC MGIT960 culture and Xpert MTB/RIF assay using bronchoalveolar lavage fluid and sputum.Drug sensitivity test was carried out by microplate Alarmar-Blue method in tuberculosis culture-positive patients.Firstly,based on the final clinical diagnosis as the gold standard,the tuberculosis group and the non-tuberculosis group were determined,then to compare the value of three methods in the diagnosis of pulmonary tuberculosis and the difference between the two specimens.Joint tests were conducted between specimens and detection methods to explore the best diagnostic scheme for tuberculosis.Secondly,using BACTEC MGIT960 culture as the gold standard,to explore the value of Xpert MTB/RIF assay in the diagnosis of tuberculosis,and compare the consistency between Xpert MTB/RIF assay and BACTEC MGIT960 culture.Finally,the accuracy of Xpert MTB/RIF for the detection of rifampicin resistance was investigated by using the results of microplate Alarmar-Blue susceptibility test as the gold standard.Results:General information:The newly diagnosed 167 suspected pulmonary tuberculosis patients,90 males and 77 females,aged 10-74 years,mean age(34.44±16.98)years old,130 cases of pulmonary tuberculosis,37 cases of non-tuberculosis group.Diagnostic efficacy of three detection methods for tuberculosis:The sensitivity,specificity,positive predictive value and negative predictive value of Xpert MTB/RIF using bronchoalveolar lavage fluid were 65.4%,100.0%,100.0% and 45.1% respectively,which were higher than those of acid-fast smear and BACTEC MGIT960 culture.By comparing the area under the ROC curve,the diagnostic value of BACTEC MGIT 960 and Xpert MTB/RIF in both specimens was superior to that of acid-fast staining smear,and the difference was statistically significant(P<0.05).The diagnostic value of Xpert MTB/RIF was better than BACTEC MGIT 960 when using the bronchoalveolar lavage fluid,and the difference was statistically significant(P<0.05).In the BACTEC MGIT 960 culture and Xpert MTB/RIF assay,the difference between the two specimens was not statistically significant(P>0.05).Efficacy analysis of combined test in the diagnosis of pulmonary tuberculosis:By comparing the area under the ROC curve,the BACTEC MGIT960+Xpert MTB/RIF combined detection had the highest area under the curve,compared with acid-fast staining+BACTEC MGIT960 and acid-fast staining+Xpert MTB / RIF detection,and the difference was statistically significant(P<0.05).In the bronchoalveolar lavage fluid test,the area under the BACTEC MGIT960+Xpert MTB/RIF combined test curve was larger than the single test.Compared with BACTEC MGIT960,the difference was statistically significant(P<0.001)?However,compared with Xpert MTB/RIF,the difference was not statistically significant(P>0.05).There was no significant difference between bronchoalveolar lavage fluid and sputum specimens in combination with BACTEC MGIT960+Xpert MTB/RIF(P>0.05).Combined BACTEC MGIT960+Xpert MTB/RIF,bronchoalveolar lavage fluid and sputum specimens were showed no statistically significant difference(P>0.05),and the difference between single and combined specimens was statistically significant(P<0.001).Analysis of the mycobacterium tuberculosis load by Xpert MTB/MTB assay:In the tuberculosis culture-negative bronchoalveolar lavage fluid samples,17 samples of M.tuberculosis were detected by Xpert MTB/RIF,which the load of mycobacterium tuberculosis was mainly very small and small.Consistency analysis of Xpert MTB/RIF assay and tuberculosis culture:When the BACTEC MGIT 960 culture results were used as the gold standard,the sensitivity,specificity,positive predictive value and negative predictive value of Xpert MTB/RTF using bronchoalveolar lavage fluid were 91.9%,69.6%,80.0% and 86.7%,respectively.The consistency of Xpert MTB/RTF and BACTEC MGIT 960 was moderate.Analysis of the detection of rifampicin resistance in mycobacterium tuberculosis by Xpert MTB/RIF assay : When the results of drug sensitivity test by microplate Alarmar-Blue method were used as gold standard,the consistency coefficient of Xpert MTB/RTF and drug susceptibility test for rifampicin in both samples was greater than0.75.The Xpert MTB/RIF and microplate Alarmar-Blue method showed good consistency in the detection of rifampicin resistance.Conclusion:1.The Xpert MTB/RIF assay using bronchoalveolar lavage fluid has a high application value in clinical diagnosis of pulmonary tuberculosis and a high accuracy in the detection of rifampicin resistance.It can be recommended for primary screening of patients which be suspected pulmonary tuberculosis.2.The combined detection of Xpert MTB/RIF and BACTEC MGIT960 culture,as well as the combined detection of specimens,can further improve the diagnostic accuracy of pulmonary tuberculosis.