Abstract:

Objective: To analyze the value of GeneXpert MTB/RIF (GeneXpert) in improving the pathogenic positivity and early diagnosis of rifampicin resistance of pulmonary tuberculosis in primary tuberculosis prevention and treatment institution in Beijing. Methods: A retrospective analysis was performed on 3060 pulmonary tuberculosis suspects who visited the Tuberculosis Outpatient Department in Chaoyang District of Beijing from 2018 to 2022. The positive rates of acid-fast bacilli smear microscopy, Löwenstein-Jensen medium based solid culture for mycobacterium (solid culture), and GeneXpert among tuberculosis suspects, as well as the positive proportion of each testing method among overall laboratory confirmed patients were analyzed. The sensitivity and specificity of GeneXpert was analyzed in sputum samples using solid culture as a reference standard. The value of GeneXpert for detection of rifampicin resistance was also analyzed. Results: From 2018 to 2022, the laboratory confirmed cases in active pulmonary tuberculosis cases gradually increased from 45.07% (215/477) in 2018 to 69.39% (102/147) in 2022, with statistical significance ( {\chi }_{\mathrm{t}\mathrm{r}\mathrm{e}\mathrm{n}\mathrm{d}}^2=27.761, P<0.001). The positive rate of acid-fast bacilli smear microscopy (46.51%, 347/746), mycobacterial solid culture (83.24%, 621/746), and GeneXpert (82.71%, 617/746) among all laboratory confirmed pathogenic positive cases was statistically different (χ²=320.000, P<0.001). Among all pathogenic positive cases, the proportion of smear-negative and GeneXpert-positive cases was 36.86% (275/746), and smear-negative/solid culture-negative but GeneXpert-positive cases were 12.60% (94/746), respectively. The sensitivity and specificity of GeneXpert were 79.39% (493/621; 95%CI: 76.20%-82.56%) and 93.39% (1751/1875; 95%CI: 92.27%-94.51%), respectively. The total rifampicin resistance rate of pulmonary tuberculosis patients detected by GeneXpert was 7.46% (46/617). The frequency of each mutation probe was as follows: probe E (63.27%, 31/49) >combined mutation (AB, AD, DE and ABE, 10.20%, 5/49) >probe D (8.16%, 4/49) >probe A (6.12%, 3/49) =probe B (6.12%, 3/49) >no probe mutation (4.08%, 2/49) >probe C (2.04%, 1/49). Conclusion: In primary tuberculosis prevention and treatment institution, the application of GeneXpert combined with mixing three sputum samples can help improve the pathogenic positive rate of pulmonary tuberculosis patients, and early detect the rifampicin-resistant patients.

Key words: Tuberculosis, pulmonary, Molecular diagnostic techniques, Drug resistance, Sensitivity and specificity, Comparative study