Evaluation Of Methodological Effectiveness For Detection Of Mycobacterium Tuberculosis In Clinical Laboratory

Objective:To evaluate the effectiveness of different laboratory methods in the diagnosis of pulmonary tuberculosis(PTB),to provide data reference for the early diagnosis of PTB.Methods:Different methodological comparison studies were used.Sputum acid-fast staining,MGIT culture,Xpert MTB/RIF test were used for suspected tuberculosis patients admitted to Tong Ren Hospital.The sensitivity and specificity were compared by chi-square test.?-interferon released at different time points after stimulation of M.tuberculosis antigen in whole blood was detected by ELISA.Parallel experiments were performed to detect the percentage of IFN-?~+CD4~+T,IFN-?~+CD8~+T lymphocytes in peripheral blood by multicolor flow cytometry.Results:The sensitivity of acid-fast staining,MGIT liquid culture,Xpert MTB/RIF test and the three methods combination in the diagnosis of active PTB were 45.7%(63/138),63.8%(88/138),65.4%(87/133),78.2%(104/133)respectively.The sensitivity of MGIT culture and Xpert MTB/RIF test were significantly higher than that of acid-fast staining(?~2 was 35.79,11.26,respectively,all P<0.01).There was no significant difference in sensitivity between MGIT liquid culture and Xpert MTB/RIF test(?~2 was 29.87,P>0.05),meanwhile the sensitivity of combined detection is higher than that of single detection(?~2 was30.84,64.62,70.14,respectively,all P<0.01).The diagnostic specificity were 99.1%(116/117),98.3%(115/116),99.1%(113/114)and 97.3%(110/113)respectively.There was no significant difference in the specificity of these three methods.After the tuberculosis antigen stimulated,the percentage of CD4~+T and CD8~+T lymphocytes expressing IFN-?was(0.508±0.210)%and(0.543±0.176)%in the tuberculosis group,higher than that in the normal control group.IFN-?at different time points in the tuberculosis group was also higher than that in the normal control group by ELISA(P<0.01).Conclusion:MGIT culture and Xpert MTB/RIF show higher sensitivity for PTB detection.Combined detection can improve detection sensitivity.CD4~+T cells and CD8~+T lymphocytes expressing IFN-?after stimulation by specific antigen can be accurately distinguished by FCM,which has a good auxiliary value for IFN-?release assay.