Evaluation of Xpert MTB/RIF assay for the diagnosis of extrapulmonary tuberculosis in Southwest China

The purpose of this study was to determine the diagnostic efficacy of Xpert MTB/RIF assay for rapid diagnosis of Tuberculosis (TB) and detection of rifampicin (RIF) resistance in patients suspected of having EPTB, assessing it against traditional culture and drug susceptibility test (DST) by proportional method, and the ability to predict multidrug resistance TB by Xpert MTB/RIF assay. In this study, the Xpert MTB/RIF assay was applied to 1,614 extrapulmonary specimens. Compared with TB culture and Composite Reference Standard (CRS), the Xpert MTB/RIF assay had a high sensitivity and specificity for detection of EPTB. Depending on the culture method or CRS as the standard, sensitivity of the Xpert MTB/RIF assay for detection of MTB in pleural effusion, cerebrospinal fluid, thoracic drainage fluid and throat swabs specimens were lower than that of other specimens. According to the experimental results, we have reason to believe that Xpert MTB/RIF assay is a rapid and simple technique with high sensitivity and specificity for diagnosing EPTB and detecting drug resistance in variety of specimens. Xpert MTB/RIF assay combined with DST maybe identify more cases of multi-drug resistant tuberculosis (MDR-TB). Author summaryTuberculosis (TB) is the second most deadly infectious disease after COVID-19. Improving the accessibility of WHO recommended rapid molecular diagnostic tests to achieve earlier and more accurate diagnosis of TB is an important part of strengthening TB laboratory work in the strategy of ending the epidemic of tuberculosis. Extrapulmonary tuberculosis (EPTB) accounts for 15% of all tuberculosis cases. Due to the unique biological samples of different classified EPTB and the occult nature of their onset, their diagnosis is more challenging. Smear microscopy is often insensitive and culture methods are prolonged. With the introduction of Xpert MTB/RIF assay (Cepheid Inc.), this has changed TB diagnostics by providing a rapid accessible platform to diagnose TB and identify rifampicin(RIF) resistance within 2h. Xpert MTB/RIF assay is a suite of semi-nested real-time fluorescent quantitative PCR in vitro diagnostic technologies with good detection efficiency. In recent years, WHO has limited recommended Xpert MTB/RIF assay to detect various types of samples other than sputum for preliminary diagnosis of EPTB. The purpose of this paper is to systematically evaluate the practical application effect of Xpert MTB/RIF assay in the clinical diagnosis of EPTB, and provide scientific guidance for clinicians.u