Abstract:

Objective To evaluate the clinical value of GeneXpert MTB/RIF system in diagnosis of pulmonary tuberculosis(PTB) smear-negative and rifampicin resistance.Methods Lab testing results of PTB patients in Longyan city during 2018, including sputum smear microscopy, sputum culture, GeneXpert system test, traditional drug susceptibility test (DST) and bacterial identification, were collected from the laboratory registration and corrected with the information of patients registered in the Tuberculosis Management Information System. Six hundred and fifty nine results of suspected tuberculosis patients with smear-negative were collected,307 of them were detected by GeneXpert, 519 by solid sputum culture and bacterial identification, 228 by both GeneXpert and solid sputum culture. Finally 622 PTB patients with smear-negative were clinical diagnosis. Regarding clinical diagnosis and sputum culture as standard to evaluate the sensitivity, specificity and consistency of GeneXpert in detecting MTB. Another 97 PTB patients detected by both GeneXpert and proportional DST were included to evaluate the efficacy of GeneXpert in detecting rifampicin resistance. SPSS 24.0 software were used to data management to analysis.Chi-square tests were performed to compare the detection rates of Mycobacterium tuberculosis(MTB) by different tests. P<0.05 was considered statistically significant. Results Among the 622 PTB patients with smear negative.The MTB detection sensitivity of GeneXpert system in smear negative TB patients (29.97%, 92/307) was significantly higher than that of sputum culture (7.13%, 37/519) (χ²=76.30, P<0.05). Regarding the result of clinical diagnosis as standard, the specificity of GeneXpert system was consistent with the solid sputum culture(100.00%),and the sensitivity was higher than that of solid sputum culture (31.40%(92/293) vs 7.46% (37/496)),the Kappa values were very poor(Kappa=0.037,0.007). Regarding the result of solid sputum culture and bacterial identification as standard, the sensitivity, specificity, positive predictive value and Kappa value of GeneXpert system in detecting MTB were 90.32%(28/31)、77.00%(154/200)、37.84%(28/74)、98.09%(154/157) and 0.420, respectively. There was no significant difference between Genexpert (9.28%,7/97) and proportionate drug sensitivity (6.18%, 6/97) in detecting rifampicin resistance of 97 PTB patients(χ²=0.00, P>0.05). Conclusion GeneXpert system has a good performance in detecting MTB with smear-negative patients, as well as the rifampicin resistance MTB. Therefor it could be recommended as a rapid clinical diagnostic method for smear-negative tuberculosis and rifampicin-resistant tuberculosis in primary designated tuberculosis hospitals.

Key words: Tuberculosis, pulmonary, Nucleic acid probes, Laboratory techniques and procedures, Microbial sensitivity tests, Resistance, bacterial, Rifampin, Comparative study