The diagnostic value of liquid-based cytology of pleural fluid in malignant pleural effusion: A prospective study

Introduction: Pleural effusion (PE) is commonly observed in clinical practice. Conventional smear (CS), cell block (CB), and liquid-based cytology (LBC) of pleural fluid are used to guide the diagnosis of malignant pleural effusion (MPE). However, the effectiveness of these cytological techniques, whether used alone or in combination, is still not well established. Methods: A prospective study was conducted from October 2019 to May 2020 at the Department of Pulmonary Medicine, Cho Ray Hospital (Ho Chi Minh City, Vietnam). Suspected MPE patients were investigated by simultaneous cytological methods (CS, CB, and LBC) of pleural fluid and pleural tissue histopathology. The study included 47 patients with MPE, confirmed by pleural tissue pathology as the gold standard. The study compares the sensitivity of the three cytological methods. Results: Out of 69 patients suspected of MPE, 47 were confirmed to have MPE through histopathological analysis of pleural biopsy. The average age of the study participants was 62.6 years, with 44.7% being male. The sensitivity of LBC and CB, LBC and CS, and CB and CS did not significantly differ, with p-values of 0.546, 0.789, and 0.606, respectively (McNemar test). Combining two of the three cytological methods (CS, CB, LBC) significantly enhances the sensitivity in diagnosing MPE compared to using a single method alone, except for the combination of CB and LBC versus LBC alone. The study has limitations, including the exclusion of non-MPE pleural effusion cases, which means the specificity of the cytological methods could not be calculated. Additionally, the limited number of patients should be taken into consideration, and caution is advised when interpreting the study results. Conclusions: The study concludes that CS, CB, and LBC methods have similar sensitivity in diagnosing MPE. Combining any two methods improves diagnostic sensitivity compared to using a single method, although CB and LBC together do not surpass LBC alone. Clinicians should consider combining cytological techniques to optimize the diagnostic sensitivity of MPE.