Performance Assessment of Xpert MTB/RIF Assay for Detecting Pulmonary Tuberculosis and Rifampin Resistance in a Tertiary Care Hospital in Korea

• Published in: Japanese Journal of Infectious Diseases Vol. 74; no. 6; pp. 537 - 542
• Main Authors: Chang, Jeonghyun, Sung, Heungsup, Jo, Kyung-Wook, Shim, Tae Sun, Kim, Mi-Na
• Format: Journal Article
• Language: English
• Published: Japan National Institute of Infectious Diseases, Japanese Journal of Infectious Diseases Editorial Committee 22.11.2021; Japan Science and Technology Agency
• Subjects: AFB smear; Antibiotics, Antitubercular - therapeutic use; Assaying; Bacilli; Drug Resistance, Bacterial - genetics; Humans; Incidence; mycobacterial culture; Mycobacterium tuberculosis; Mycobacterium tuberculosis - drug effects; Mycobacterium tuberculosis - genetics; Mycobacterium tuberculosis - isolation & purification; Performance assessment; Polymerase Chain Reaction - methods; Republic of Korea - epidemiology; Retrospective Studies; Rifampin; Rifampin - pharmacology; Rifampin - therapeutic use; rifampin resistance; Sensitivity analysis; Sensitivity and Specificity; Sequence Analysis, DNA - methods; Sputum - microbiology; Tertiary Care Centers; Tuberculosis; Tuberculosis, Pulmonary - diagnosis; Tuberculosis, Pulmonary - drug therapy; Xpert MTB/RIF; Republic of Korea; AFB smear; mycobacterial culture; Xpert MTB/RIF; rifampin resistance; Mycobacterium tuberculosis
• ISSN: 1344-6304; 1884-2836
• DOI: 10.7883/yoken.JJID.2020.978

In this study, we aimed to assess the performance of the Xpert MTB/RIF assay for the detection of pulmonary tuberculosis compared to the acid-fast bacilli (AFB) smear and culture analysis, and the incidence of rifampin resistance using the drug susceptibility test. The specimens referred for AFB smear and culture analysis and Xpert MTB/RIF assay from April 2015 to March 2018 were retrospectively reviewed. The sensitivity, specificity, and mean cycle threshold (Ct) values obtained in Xpert MTB/RIF assay and for rifampin resistance were analyzed. The results of Xpert MTB/RIF assay for pulmonary tuberculosis were evaluated based on the AFB smear grade. Among 3,840 specimens, 491 were positive in Xpert MTB/RIF assay and 626 in culture analysis. The sensitivity and specificity of Xpert MTB/RIF assay were 75.6% and 99.4%, respectively. The sensitivity of Xpert MTB/RIF assay for smear-positive/culture-positive specimens was 98.6% and that of smear-negative and -trace/culture-positive specimens was 63.1%. The positivity of Xpert MTB/RIF assay for culture-positive specimens was 89.9%, 98.6%, 95.7%, 100.0%, and 100.0% for the smear grades trace, 1+, 2+, 3+, 4+, respectively. The Ct values of 491 specimens significantly decreased as the AFB smear grade increased (P < 0.0001). The Ct values of smear-positive, -trace, and -negative specimens were 21.7 ± 4.2, 26.5 ± 3.9, and 27.4 ± 3.6, respectively. Rifampin resistance evaluated using Xpert MTB/RIF assay and culture analysis exhibited a correlation of 98.3%. The region covered by probe E was the most frequently mutated region (50.0%). Xpert MTB/RIF assay demonstrated reliable performance in detecting pulmonary tuberculosis from smear-positive and culture-positive specimens; however, further improvements are still required to detect smear-negative and culture-positive specimens.