Han Na Lee, Jung Im Kim, Yee Hyung Kim
Abstract
Purpose
To determine the diagnostic accuracy of the Xpert MTB/RIF assay in patients with smear-negative pulmonary tuberculosis (TB) and to assess clinical and CT characteristics of Xpert-negative pulmonary TB.
Introduction
Tuberculosis (TB) remains a critical cause of death among infectious disease worldwide. In 2018, 10 million people fell ill and over 1.5 million people died of TB, which is a preventable and curable disease [1]. Therefore early detection and appropriate treatment are important for effective control of TB transmission.
For TB diagnosis, sputum acid-fast bacilli (AFB) smear is easy to perform, but it shows low sensitivity of 50–70% for culture positive TB [2, 3]. Although culture is considered the reference standard for TB diagnosis, it is time-consuming and takes 6 and 8 weeks on liquid and solid culture media, respectively [4, 5]. Therefore molecular diagnostic methods, such as real-time polymerase chain reaction (PCR) assay and Xpert MTB/RIF (Cepheid; Sunnyvale, USA) assay, have been developed and are widely used for early detection of TB with higher sensitivity.
Materials and methods
Patient selection
This study was approved by the Institutional Review Board of Kyung Hee University Hospital at Gangdong (2020-09-024), and the need for informed consent was waived. Patients’ medical records were fully anonymized before the 6-months examination period. We retrospectively reviewed the medical records of all adult patients with clinically suspicious pulmonary TB for whom sputum smears for AFB and sputum Xpert/MTB assay were performed between September 1, 2014 and February 28, 2020.
Diagnosis of pulmonary TB was defined by the culture of M. tuberculosis from sputum or other specimens, such as bronchoscopic specimen or lung tissue obtained by percutaneous transthoracic needle biopsy. Culture-negative pulmonary TB was defined as patients with suspected radiologic and respiratory symptoms and negative culture for M. tuberculosis for three initial sputum or other specimens [15] and who met one of the following inclusion criteria: (1) positive TB-PCR on sputum and/or bronchoscopic specimen and/or lung tissue, and (2) radiologic improvement on anti-tuberculosis medication. Patients with loss to follow-up during TB medication for culture-negative TB and who took TB medication before examination of Xpert MTB/RIF assay were excluded from the analysis.
Discussion
Xpert MTB/RIF test has developed rapid diagnosis of pulmonary TB and MDR-TB cases [18]. We evaluated the diagnostic yield of sputum Xpert MTB/RIF in suspected smear-negative TB patients, because the results of sputum Xpert MTB/RIF for smear-negative patients is more relevant in clinical practice. To the best of our knowledge, this is the first study to compare CT findings of pulmonary TB cases according to sputum Xpert MTB/RIF positivity. We also suggested CT imaging findings associated with false-negative TB, which may help to decide whether further work-up is needed or whether it should be treated with anti-TB medication for patients with suspected TB, but who have negative results on the sputum AFB and Xpert MTB/RIF tests.
Citation: Lee HN, Kim JI, Kim YH (2021) Clinical and CT characteristics of Xpert MTB/RIF-negative pulmonary tuberculosis. PLoS ONE 16(5): e0250616. https://doi.org/10.1371/journal.pone.0250616.
Editor: Mohammad Mehdi Feizabadi, School of Medicine, Tehran University of Medical Sciences, ISLAMIC REPUBLIC OF IRAN
Received: December 22, 2020; Accepted: April 9, 2021; Published: May 3, 2021.
Copyright: © 2021 Lee et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: All relevant data are within the paper and its Supporting information files.
Funding: This study was supported by a grant from Kyung Hee University in 2020 (KHU-20201238).
Competing interests: The authors have declared that no competing interests exist.
