Eosinophilia in Pleural Effusions: a Speculative Negative Predictor for Malignancy

Abstract

Background: Eosinophilic pleural effusion (EPE) is an eosinophil count more than 10% on cytology of pleural samples. Recently, it was reported that malignancy had been the most prevalent cause inducing EPE. Therefore, we conducted an analysis on the prevalence and etiology of EPE and investigated the relationship between EPE and malignancy. Materials and Methods: Data for pleural cell differential count from patients receiving thoracentesis during the period from January 2008 to December 2013 were compared with clinical data and established diagnosis of patients obtained via electronic chart review. Results: A total of 6,801 requests of pleural cytology from 3,942 patients with pleural effusion who had received thoracentesis were available at Far Eastern Memorial Hospital from 2008 to 2013, and of these subjects, 115 (2.9%) were found to have EPE. The most frequent cause of EPE was malignancy (33.0%, n=38), followed by parapneumonic effusions (27.8%, n=32), tuberculosis pleuritis (13.9%, n=16), transudate effusions (12.2%, n=14) and the presence of blood or air in pleural space (10.4%, n=12). Additionally, an inverse relationship of eosinophilia in pleural fluid was identified in patients with malignancy and EPE. The cut-off eosinophil count in pleural fluid was 15% for the most accurate discrimination between malignancy and benign disorders in patients with EPE. At the cut-off level, the sensitivity and specificity were 65.8% and 67.5%, respectively. Conclusions: Pleural fluid eosinophilia was a speculative negative predictor for malignancy, despite the fact that cancers, including lung cancers and metastatic cancers to lung, were the most leading cause of pleural fluid eosinophilia. An inverse correlation was observed between the pleural eosinophil percentage and the likelihood of malignancy in patients with EPE.

A narrative review of malignant eosinophilic pleural effusion: incidence, etiology and prognostic significance

“…The cumulative incidence of malignancy among EPEs has gradually increased from 7% to 25% over the last 4 decades (2). The current studies confirmed that malignancy was the most common etiology related to EPE (ranging from 22.7% to 40.1%) (2,7,13,18,22). The tendency may be explained by the development of diagnostic technology, improved diagnostic awareness, disparity of study population, or various disease spectrum over time.…”

“…The likelihood of malignancy was only 7% when an eosinophil count was more than 32% (2). Similarly, Chu et al (22) found that eosinophil count in pleural effusion was a speculative negative predictor for malignancy in patients with EPE when eosinophils exceeded 15%. The analysis of Krenke et al (7) revealed that an eosinophil percentage of 40% was the most accurate cut-off level to differentiate between malignant and nonmalignant EPE, which supported the study by Kuhn et al (3) who suggested that eosinophils exceeded 50% in the pleural fluid possessed the strongest negative predictability towards malignancy.…”

“…However, the proportions were far below those observed by Kuhn et al (3) who utilized the same approach and found that the probability of malignancy was 40% from 47%. Hence, when evaluating the results, the disease spectrum of the study population should be given serious consideration (5,22). Various outcomes of MEPE prevalence were mere reflections of the population investigated.…”

Incidence, aetiology and clinical features of eosinophilic pleural effusion: a retrospective study

“…The percentages were similar to those in previous studies, which reported 12.6% [ 4 ] and 10% [ 2 ], but higher than those in two other studies, which indicated 5–8% [ 2 ] and 7.2% [ 7 ]. However, Chu FY found that the morbidity of EPE was only 2.9% [ 6 ]. The discrepancy may be attributed to different populations, epidemic characteristics, test methods or the timing of pleural fluid collection.…”

Pleural fluid biochemistry: A first step toward an etiological diagnosis of pleural effusions

“…In a recent systematic review that included 687 cases of eosinophilic PEs, the most frequent causes were neoplasms (26%), idiopathic (25%), parapneumonic (13%), blood or air in the pleural cavity (13%), tuberculosis (7%), and transudates (7%), among a variety of additional causes 33 . As the percentage of eosinophils in the PF increases (e.g., > 30%), the probability of a neoplasm decreases while the probability of idiopathic causes increases 33,34 . For instance, neoplasms only explained 7% of the PEs with eosinophil counts > 32% in the aforementioned systematic review 33 .…”