Abstract:

Objective: To evaluate the diagnostic performance of GeneXpert MTB/RIF Ultra (referred to as “Xpert Ultra”) in detecting sputum samples for newly diagnosed pulmonary tuberculosis. Methods: A total of 443 suspected new cases of pulmonary tuberculosis patients who visited the Shandong Public Health Clinical Center from July 2019 to May 2022 were collected as research subjects. After comprehensive clinical diagnosis, there were 243 cases in the pulmonary tuberculosis group and 200 cases in the non-pulmonary tuberculosis group. After collecting sputum samples from the research subjects, they were subjected to fluorescence staining smear microscopy, BACTEC MGIT 960 liquid culture (referred to as “MGIT 960 culture”), Xpert Ultra, and GeneXpert MTB/RIF (referred to as “Xpert”) detection; MGIT 960 cultured positive samples were further subjected to strain identification. Sputum samples from 231 patients (125 in the tuberculosis group and 106 in the non-pulmonary tuberculosis group) were simultaneously subjected to Xpert Ultra direct detection and centrifugal precipitation treatment. Using the clinical comprehensive diagnosis results and MGIT 960 culture results as reference standards, evaluate the diagnostic value of the above methods for newly diagnosed pulmonary tuberculosis. Results: Using clinical comprehensive diagnosis as the reference standard, the sensitivity and specificity of Xpert Ultra were 68.72% (167/243) and 100.00% (200/200), respectively. The sensitivity of Xpert Ultra was higher than smear fluorescence staining microscopy (36.63% (89/243)) and MGIT 960 culture (62.14% (151/243)), and the differences were statistically significant (χ²=54.830, P<0.001; χ²=3.198, P<0.05). The AUC of Xpert Ultra was the largest, which was 0.809, and highly consistent with clinical comprehensive diagnosis (Kappa value of 0.66). Using MGIT 960 culture as the reference standard, the sensitivity and specificity of Xpert Ultra were 94.70% (143/151) and 94.52% (276/292), respectively. The sensitivity of Xpert Ultra was higher than smear fluorescence staining microscopy (60.26% (91/151)) and Xpert (90.07% (136/151)), and the differences were statistically significant (χ²=13.411, P<0.001; χ²=3.847, P<0.05); and the AUC of Xpert Ultra was 0.946, indicating the highest diagnostic efficiency and almost identical to that of MGIT 960 culture (Kappa value of 0.88). Xpert Ultra can accurately distinguish between Mycobacterium tuberculosis and nontuberculous mycobacteria, and its “trace” results could serve as a diagnostic basis for newly diagnosed pulmonary tuberculosis. For the 231 patients’ sputum samples, direct testing and testing after centrifugal sedimentation were performed, and using clinical comprehensive diagnosis as the reference standard, it was found that the sensitivity of Xpert Ultra testing on sedimented sputum samples (80.00%, 100/125) was 12.00% higher than that of direct testing on sputum samples (68.00%, 85/125); in the tuberculosis group, 31.20% (39/125) of the samples showed at least a one-log increase in semi-quantitative results. Conclusion: Xpert Ultra testing of sputum samples has good diagnostic performance for newly diagnosed pulmonary tuberculosis and is of significant value for its rapid diagnosis and treatment.

Key words: Tuberculosis, pulmonary, Sputum, Diagnosis, differential, Molecular diagnostic techniques