Diagnostic value and safety of medical thoracoscopy in undiagnosed pleural effusions-a prospective observational cohort study.

Background: With the need for "actionable histology" in the current era of targeted cancer treatment, and the increasing practice of upfront thoracoscopy (without a prior diagnostic thoracentesis) or a "biopsy first" approach in suspected malignant pleural effusions (MPEs), we sought to prospectively evaluate the diagnostic accuracy, including full molecular profiling of cancer, and safety of medical thoracoscopy (MT) at a tertiary referral hospital. Methods: Patients with MT performed for an undiagnosed pleural effusion between January 2020 and December 2022 were included in this observational cohort study. All procedures were performed with a semirigid thoracoscope under conscious sedation. Clinical outcomes and adverse events were recorded prospectively. Results: We evaluated 141 patients, with a mean age of 67±12 years. Talc poudrage was performed in 67 (47.5%) patients with a median of 2 [interquartile range (IQR), 1-4] hospitalisation days after MT. Upfront thoracoscopy was performed in approximately half (55.3%) of patients. The overall diagnostic accuracy of MT was 95.7% in our cohort. A final diagnosis of cancer was made in 116 (82.3%) patients, with lung (67.2%) and breast cancer (8.6%) the most common. The diagnostic sensitivity of MT for malignancy was 94.8%, and molecular profiling of relevant cancer types for oncogenic mutations was achieved in all patients with malignancy seen on histopathology. The most common non-malignant diagnosis was tuberculous pleuritis in 14 patients (9.9%). Major complications occurred in 3 (2.1%) patients. Two patients had re-expansion pulmonary edema that resolved with low flow oxygen supplementation in the general ward, and one patient required intensive care unit admission for cardiac tamponade from a malignant pericardial effusion. There were no cases of mortality, bleeding complications or persistent air leaks. Conclusions: MT is a well-tolerated and effective option for the evaluation of undiagnosed pleural effusions. With expanding utility and expertise with MT and other pleural interventions, the challenge for respiratory physicians is integrating these into expeditious diagnostic and effective therapeutic pathways, individualised to patients' needs.