Role of Medical Thoracoscopy in undiagnosed exudative pleural effusion with low Adenosine Deaminase level: Prospective Observational study in a tertiary care hospital from Eastern India

Background: Establishing the etiology of exudative pleural effusions in low ADA level (<40IU/L) often requires biopsies from the pleura. Medical thoracoscopy (MT) is a minimally invasive procedure performed under local anesthesia.
Aim: To assess diagnostic yield of medical thoracoscopy in undiagnosed exudative pleural effusion with low ADA (<40 IU/L). To detect the association of pleural fluid ADA in different thoracoscopic diagnosis.
Methods: This was a prospective observational study over a period of one year. Patients with undiagnosed exudative pleural effusion were enrolled in the study. MT was performed with rigid thoracoscope (OptymetCE0197) under local anesthesia. ADA level of pleural fluid was noted. Pleural biopsy material was subjected to histopathology examination and culture for mycobacteria along with cartridge‑based nucleic acid amplification test for TB. Incidence of percentage of tuberculosis and malignancy in low ADA level was calculated.
Results: 106 patients with undiagnosed exudative pleural effusion underwent thoracoscopy of which were 56 male and 50 female. MT was able to establish the diagnosis in 96 cases, providing a diagnostic yield of 90.5%. Pleural TB contributed to 35.8% of undiagnosed pleural effusions in the present study. The mean ADA value was 33.9 and 19.6 in tuberculosis and malignant pleural effusion respectively which was found to be statistically significant. Among patients diagnosed as tuberculosis Mycobacterial Tuberculosis was detected on CBNAAT in 18%, while CBNAAT was negative in 82% cases. A cut off 28.5 IU/L for pleural fluid ADA, the sensitivity and specificity were 88.5% and 76.7% respectively based on receiver‑operating characteristic analysis (AUC0.88).
Conclusion: Medical Thoracoscopy is a valuable diagnostic tool for undiagnosed exudative pleural effusion. It is a simple and safe procedure without significant morbidity and mortality. Thoracoscopy should be done as soon as possible in low ADA value whenever it is available. As significant number of tuberculosis patients are seen in even in low ADA(<40IU/L) setting.