Performance of Xpert® MTB/RIF in diagnosing tuberculous pleuritis using thoracoscopic pleural biopsy

Etiological diagnosis of tuberculous pleuritis is challenging, owing to a paucity of Mycobacterium tuberculosis (MTB) in the affected region. Moreover, currently available methods, such as the detection of acid-fast bacilli and microbiological culture, are not always conducive to timely diagnosis and treatment. In this study, we evaluated the performance of Xpert® MTB/RIF assay (hereinafter referred to as "Xpert") in detecting MTB in difficult-to-diagnose patients using suspensions of pleural biopsy tissue specimens obtained under direct thoracoscopic guidance.

One hundred and sixty patients with an unexplained pleural effusion were included from the Shenyang Tenth People's Hospital and Shenyang Chest Hospital, China, between 2017 and 2018. The included patients underwent thoracoscopy under local anesthesia, with an intercostal incision of approximately 1.0 cm for biopsy. The biopsy specimens were used for pathological and etiological examinations. The Xpert test was evaluated for its sensitivity and specificity, as well as positive and negative predictive values (PPV and NPV, respectively), against data obtained using standards: the BACTEC™ MGIT™ 960 liquid culture system and a composite reference standard (CRS).

The sensitivity and specificity of Xpert were 68.8 and 64.6%, respectively, against the MGIT 960 culture data. The PPV and NPV of Xpert were 56.4 and 75.6%, respectively. The sensitivity of Xpert was 69.0% against the CRS data, which was significantly higher than that of MGIT 960 culture (56.6%). The PPV and NPV of Xpert against the CRS data were 100.0 and 57.3%, respectively.

Xpert is a good rule-in test but has limited value as a rule-out test for the diagnosis of tuberculosis pleuritis.