Improving the Yield of Diagnostic Medical Thoracoscopy for Undiagnosed Exudative Pleural Effusions Using a Rigid Diagnostic Algorithm
Authors: Augustine Jolsana , Vijay Anand , Ramachandran Divya , Cleetus Melcy , Nirmal Aparna Soman , John Susan , Thomas Sunitha , Venkitakrishnan Rajesh 
Published: December 2021

Background:
Establishing the etiology of exudative pleural effusions in the setting of an unrewarding pleural fluid analysis often requires biopsies from the parietal pleura. However, it may be noted that diagnosis such as pulmonary embolism and connective tissue diseases can result in an exudative pleural effusion where a pleural biopsy can yield nonspecific results. Medical thoracoscopy (MT) is a minimally invasive procedure performed under local anesthesia or moderate sedation with excellent yield and favorable safety profile. We analyzed the diagnostic yield of MT for exudative pleural effusions after employing a rigid diagnostic algorithm. The study was undertaken to ascertain the yield of MT in establishing the diagnosis in diagnosis of exudative pleural effusions, to find out the relative contribution of pleural tuberculosis (TB) as a cause of undiagnosed exudative pleural effusion, to describe the etiology of undiagnosed exudative pleural effusion in patients undergoing MT and to determine the correlation between pleural fluid adenosine deaminase (ADA) levels and TB pleuritis in patients undergoing MT.

Methods:
This was a retrospective study. Patients with undiagnosed exudative pleural effusion were included in the study. MT was performed with semirigid thoracoscope (Olympus LTF 160) under local anesthesia and conscious sedation. Gross appearance and ADA level of pleural fluid were noted. Pleural biopsy material was subjected to histopathology examination and culture for mycobacteria along with cartridge-based nucleic acid amplification test for TB. The yield of MT for establishing the etiology of pleural effusion and the relative contribution of tuberculous pleuritis as a cause of undiagnosed pleural effusion was ascertained. Correlation of pleural fluid ADA levels was done with a final diagnosis of TB pleuritis in patients undergoing MT.

Results:
Twenty-five patients with undiagnosed exudative pleural effusion underwent thoracoscopy of which 16 were male and 9 were female. MT was able to establish the diagnosis in all cases, providing a diagnostic yield of 100%. Histopathological examination of biopsy specimens yielded a diagnosis of malignant involvement of pleura in 10 patients and granulomatous pleuritis consistent with TB in 14 patients. Pleural TB contributed to 60% of undiagnosed pleural effusions in the present study. The mean ADA value among those who turned positive was 56.338 and 35.300 among those who turned negative using genexpert, which was found to be statistically significant. A value of 31 IU/L showed a sensitivity of 93.3% and specificity of 99.8% and hence can be taken as a cut off value for the diagnosis of pleural TB based on receiver-operating characteristic analysis.

Conclusion:
TB contributed to 60% of undiagnosed exudative pleural effusions in the present study. MT had 100% yield in the diagnosis of undiagnosed exudative effusions. Pleural fluid ADA levels may help in differentiating TB versus malignant effusion.