Diagnostic accuracy of pleural fluid cytology compared to pleural biopsy histology obtained via thoracoscopy

Introduction Pleural effusion is a common problem with a wide range of differential diagnosis including serious underlying pathology. Pleural fluid sampling is the first line investigation in the diagnostic pathway of unilateral suspected exudative effusion. Previous studies have shown mean sensitivity of about 60% for malignancy on pleural fluid cytology. In those with unclear etiology, pleural biopsy is undertaken to confirm the diagnosis. We wished to look at the diagnostic accuracy of pleural fluid cytology compared to pleural biopsy obtained on histology. Methods Retrospective analysis of consecutive patients with unilateral pleural effusion who had semi rigid thoracoscopy and pleural biopsy between January 2008 to February 2012. Results 112 patients had thoracoscopy during the above period. Mean age was 74; male 96 (86%). 95(85%) had confirmed malignancy on pleural biopsy and 17(15%) were benign. Mesothelioma was the common 44%. Pleural cytology obtained at the time of Thoracoscopy was sent in 99 cases; malignancy was reported in 59 (60%). The sensitivity, specificity and the negative predictive value of the pleural fluid was 70% (CI: 59 to 80), 100% (CI: 78 to 100), and 37% (CI: 27 to 54) Conclusion Our results show similar diagnostic accuracy for pleural fluid cytology compared to the previous studies. This should be undertaken as the first line prior to undertaking more invasive assessment and pleural biopsy. Reference: 1. BTS guidelines for the investigation of a unilateral pleural effusion in adults Thorax 2003;58(Suppl II):ii8–ii17.