Thoracoscopic pleural biopsy improves yield of Xpert MTB/RIF for diagnosis of pleural tuberculosis

Abstract

Background and objective: Extrapulmonary tuberculosis (EPTB) accounts for ~15% of all TB patients, and TB pleural effusion is the second most common site of EPTB. The diagnosis of pleural TB is challenging due to the pauci-bacillary nature of the disease. Histopathology of thoracoscopically obtained pleural biopsy provides the highest diagnostic yield. The Xpert MTB/RIF assay (Xpert) is a PCR test that can identify both Mycobacterium tuberculosis (MTB) and rifampicin resistance. Currently, there is a lack of clarity regarding the value of Xpert on pleural tissue. We report our experience of using Xpert on thoracoscopic pleural biopsy samples.

Methods: We retrospectively reviewed the records of patients who underwent thoracoscopy in our institution over a 1-year period. Relevant clinical details; indications; and results of tests on pleural tissue and fluid, including histopathology, mycobacterial cultures and Xpert, were extracted.

Results: Of the 156 patients who underwent thoracoscopy, 73 (47%) had TB, 66 (42%) malignancy and 17 (11%) other conditions. Histopathology was diagnostic in all the 73 TB patients (100%). The yields of the microbiological tests against histopathology on thoracoscopic biopsy sample and pleural fluid were: pleural tissue Xpert 45%, pleural tissue culture 39%, pleural fluid culture 17% and pleural fluid Xpert 14%. Pleural tissue provided higher yields than fluid in both Xpert and culture (P < 0.05). Pleural tissue Xpert provided a higher yield than culture and substantially improved yield compared with closed pleural biopsy as we previously reported.

Conclusion: Thoracoscopic pleural biopsy results in increased sensitivity on Xpert testing.

Keywords: pleural disease; pleural effusion; polymerase chain reaction; thoracoscopy; tuberculosis.