Diagnostic utility of pleural fluid eosinophilia

Our plain-English summary of Diagnostic utility of pleural fluid eosinophilia, by M. Adelman, S.M. Albelda, J. Gottlieb, et al (The American Journal of Medicine, 1984).

The study

• Authors: M. Adelman, S.M. Albelda, J. Gottlieb, E.F. Haponik
• Journal: The American Journal of Medicine
• Published: 1984;77(5):915-20
• Cited by: 121 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

It has been stated that pleural fluid eosinophilia (defined as greater than 10 percent eosinophils in the pleural white cell differential count) is not helpful in the diagnosis of exudative effusions. By review of the recent literature, it was found that pleural fluid eosinophilia was associated most often with idiopathic effusions or with air previously introduced into the pleural space. Also, a high proportion of "idiopathic" and benign asbestos effusions were characterized by pleural fluid eosinophilia, a previously unrecognized phenomenon. The diagnostic utility of finding eosinophils in the pleural space was assessed from its impact on prior probabilities of disease. Estimates of pretest likelihoods of malignant versus nonmalignant pleural effusions and the prevalence of eosinophilia in effusions of known cause were obtained from extensive literature review. These were modified by using Bayes' rule to estimate the revised probability of disease in the presence of an eosinophilic effusion. The presence of pleural fluid eosinophilia considerably reduced the probability of malignancy or tuberculosis and increased the likelihood of an underlying benign disorder. Pleural fluid eosinophilia is a useful finding that can aid in the diagnosis of an exudative pleural effusion.

In plain English

This article was a review of published reports, not a new study of patients. The authors searched the literature since the early 1960s for pleural effusions (fluid around the lungs) in which eosinophils, a type of white blood cell, made up 10 percent or more of the white cells. They found 343 such cases. Of these, 74 percent fell into three groups: effusions with no cause found (35 percent), air in the pleural space (28 percent) and infection (11 percent). In the reported series, eosinophilia was found in 9 of 700 tuberculosis patients (1.3 percent), 4.9 percent of 245 cancer-related effusions, 15 of 29 benign asbestos effusions (52 percent) and 78 of 200 undiagnosed effusions (39 percent). The authors applied Bayes' rule, a method for updating a probability with new information. They estimated that eosinophilia lowered the probability of cancer from 0.39 to 0.14 and of tuberculosis from 0.17 to 0.017. It raised the probability of an asbestos-related cause from 0.03 to 0.12. The authors concluded that eosinophilia considerably reduces the probability of cancer or tuberculosis, but cautioned that it should not rule out cancer. They noted that case reports were often incomplete. They called for further study of asbestos exposure and unexplained eosinophilic effusions.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Literature review of reported cases and case series, combined with a Bayesian (Bayes' rule) probability analysis
• Who was studied: 343 published cases of eosinophilic pleural effusion found in a search of the literature since the early 1960s, plus reported series of tuberculous, malignant, benign asbestos and undiagnosed effusions. Pretest probabilities came from one prospective series of 300 effusions (Hirsch et al).
• Exposure: This was not an exposure study. The finding examined was pleural fluid eosinophilia (10 percent or more eosinophils). For benign asbestos effusion, the criteria included a history of direct or indirect asbestos exposure. No fiber types, jobs or doses were given.
• Main results:
  • Of the 343 reported eosinophilic pleural effusions, 74 percent fell into three settings: idiopathic effusions (35 percent), air in the pleural space (28 percent) and infection (11 percent).
  • Among reported tuberculous effusions, 9 of 700 patients (1.3 percent) had pleural fluid eosinophilia.
  • Among 245 reported malignant pleural effusions, the prevalence of eosinophilia was 4.9 percent.
  • Among 29 reported patients with benign asbestos effusion and pleural fluid cell counts, 15 had pleural fluid eosinophilia, with eosinophil counts above 50 percent in more than half of the reports.
  • The prevalence of eosinophilia among reported benign asbestos effusions was 52 percent.
  • Among 200 reported undiagnosed ('idiopathic') effusions, 78 had pleural fluid eosinophilia (39 percent).
  • In the Bayesian analysis, eosinophilia decreased the estimated probability of underlying malignancy from 0.39 to 0.14, and of tuberculosis from 0.17 to 0.017.
  • Eosinophilia increased the estimated probability that no diagnosis (idiopathic) would be made, from 0.21 to 0.62.
  • The estimated probability of an asbestos-related cause rose from 0.03 without eosinophilia to 0.12 with it. This passage uses the word 'asbestosis'; the table uses 'Asbestos'.
  • The pretest probabilities used were taken from one series of 300 effusions collected prospectively.
  • With eosinophilia, the relative probability of a malignant (0.14) versus nonmalignant (0.86) effusion fell to 1:6.
• The authors' conclusion: The authors concluded that finding pleural fluid eosinophilia in an exudative effusion considerably reduces the probability of malignancy or tuberculosis and increases the likelihood of an underlying benign disorder.
• Limitations the authors state:
  • Most source reports were single cases or small series.
  • Cases were often described incompletely, and definitions of pleural fluid eosinophilia varied between reports.
  • Some studies did not give the cell count from the first thoracentesis. Air introduced by earlier procedures may itself cause eosinophilia.
  • The pretest probabilities would differ from patient to patient and from institution to institution.
  • The authors cautioned that eosinophilia alone should not rule out malignancy.
  • The authors said further studies are needed on possible associations between asbestos exposure and 'idiopathic' eosinophilic pleural effusion.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Pleural plaques and thickening.

Medical terms in this study, explained in our Lexicon: Idiopathic, Pleural Effusion, Eosinophilic.

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