Laboratory diagnosis of pleural tuberculosis: An unsolved enigma

Pleural Tuberculosis (TB) diagnosis is challenging and the current diagnostic approach is multidisciplinary involving clinico-radiological methods in addition to laboratory parameters. The study aims to explore the role of all available parameters for pleural TB diagnosis.

A cross-sectional study on suspected pleural TB patients was conducted at a tertiary care hospital in Chhattisgarh from February to November 2021. After obtaining consent and clinico-radiological information, pleural fluid was collected and tested for biochemical profile and detection of Mycobacterium tuberculosis using available microbiological parameters.

Out of 170 subjects, 26 had Definite TB (Microbiologically confirmed), 22 had Probable TB (clinico-radiologically confirmed), and 122 had No-TB. Necrotizing mediastinal lymphadenopathy, cervical lymphadenopathy & loculated effusion were significant radiological findings. Amongst biochemical parameters, (Receiver Operating Characteristic (ROC) cut off 40.0 U/L; AUC = 0.889) of Adenosine Deaminase (ADA) was proved to be a better biomarker than LDH (ROC cut off 442.0 IU/L; AUC = 0.645). Out of all available microbiological parameters, Cartridge Based Nucleic Acid Amplification Test (CBNAAT) performed better by identifying (6/7; 85.71 %) pleural TB cases when compared against Microbiological Reference Standards (MRS). While compared against Composite Reference Standards (CRS), Mycobacteria Growth Indicator Tube (MGIT) performed better than other microbiological parameters by identifying (19/48; 39.5 %), while both CBNAAT and Truenat could identify (6/16; 37.5 %) and (12/32; 37.5 %) respectively.

In association with clinical and radiological features, ADA estimation is quite helpful in establishing or refuting the diagnosis of microbiologically negative pleural tuberculosis.