Utility of sending pleural fluid for cytology at the time of thoracoscopy and pleural biopsy

Background: Pleural fluid cytology is the initial investigation of choice in patients presenting with unilateral pleural effusion. Those with negative or inconclusive cytology are referred for thoracoscopy, VATS biopsy or image guided biopsy. Routinely, further pleural fluid is sent for cytology at the time of thoracoscopy. We wished to see whether this added any useful information to the pleural biopsy undertaken simultaneously in patients with unexplained unilateral pleural effusion or pleural abnormalities on CT chest. Methods: Retrospective review of consecutive patients who underwent semi-rigid thoracoscopy and pleural biopsy between January 2007 and June 2014 at Lancashire Teaching Hospitals NHS trust, Preston. Data on 300 patients was obtained and analysed. Results: Of the 300 patients, 261(87%) had pleural effusion and pleural thickening; 39(13%) had unexplained unilateral pleural effusion with no pleural abnormalities. Mean age was 74 years; male 205(68%). Pleural biopsy was positive for malignancy in 157(52%), reactive 3(1%) and non-specific inflammation 140(47%). In 157 patients with malignant pleural biopsy, pleural fluid was sent for cytology in 145 patients; 79(54%) samples showed malignant cells, 26 (18%) atypical cells and 40(28%) showed no malignant cells. In 143 patients with non-malignant pleural biopsy, pleural fluid was positive for malignant cells (adenocarcimona) in 3 patients. Conclusion: Pleural fluid cytology was positive for malignant cells in 54% of patients with malignant pleural biopsy. 3 patients had false negative pleural biopsy. Our data suggests pleural fluid analysis at the time of thoracoscopy may have added diagnostic value in a small number of patients.