Tuberculous pleuritis (TBP) is the most common manifestation of extrapulmonary TB. Its diagnosis is challenging due to the low sensitivity of mycobacterial culture from the pleural fluid and the need for invasive pleural biopsy. Preliminary data has shown the superior sensitivity of Mycobacterium tuberculosis cell-free DNA (MTB cfDNA) to conventional culture and MTB polymerase chain reaction (PCR), but the cutoff level of MTB cfDNA was not determined. This study involves a prospective collection of pleural fluid due to TBP and non-TBP aetiologies, with subsequent testing by MTB culture, MTB cfDNA and MTB PCR. The levels of MTB cfDNA in the pleural fluid will be correlated with different types of diagnosis, and its diagnostic accuracy will be compared with conventional culture and MTB PCR. A confirmatory study result of MTB cfDNA can shorten the time to diagnosis, reduce the need for pleural biopsy and prevent the delay of definitive treatment.