Investigating unilateral pleural effusions: the role of cytology.

Abstract

<b>Introduction:</b> There is uncertainty about the utility and limitations of pleural fluid cytology to diagnose malignancy. The aim of this study was to ascertain the sensitivity of cytological assessment using a large prospective cohort. <b>Methods:</b> Consecutive patients presenting with an undiagnosed unilateral pleural effusion were recruited to this UK-based observational study. All had pleural fluid sent for cytological analysis. The assessment of cytological sensitivity was based on a 12-month consultant diagnosis. <b>Results:</b> Between 2008 and 2017, 921 patients with an undiagnosed effusion were recruited, of which 515 (56%) had a malignant cause. The overall sensitivity of pleural fluid cytology to diagnose malignancy was 45% (95% C.I. 41-49). Cancer primary had a significant impact on sensitivity, with mesothelioma (15%) and lymphoma (40%) being lower than adenocarcinomas (79%), and ovarian cancer having especially high pick-up rates (95%) (p-0.02), see Figure 1. In asbestos exposed males with a unilateral exudative effusion the likelihood of diagnosing malignancy on cytology was 14%, despite a prevalence of over 60%. <b>Conclusions:</b> This is the largest prospective study of pleural fluid cytology in the literature. These results inform discussions with patients about the likely requirement for further tests after thoracentesis. In male patients with prior asbestos exposure it justifies an approach of not waiting for the cytology result prior to thoracoscopy.