Diagnostic value of total and differential leukocyte counts in pleural effusions

Our plain-English summary of Diagnostic value of total and differential leukocyte counts in pleural effusions, by T. Pettersson, H. Riska (Acta Medica Scandinavica, 1981).

The study

• Authors: T. Pettersson, H. Riska
• Journal: Acta Medica Scandinavica
• Published: 1981;210(1-2):129-35
• Cited by: 35 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Total and differential leukocyte counts in pleural fluid were determined prospectively in 140 consecutive patients undergoing diagnostic thoracentesis. The total number of leukocytes was higher in exudates than in transudates. Lymphocytes predominated overwhelmingly (more than 80% of all leukocytes) in 29 of the 31 effusions with verified or probable tuberculous etiology and in 18 of the 24 with malignant etiology, as well as in 20 exudative pleural effusions of other causes. The significant differences in the percentage of lymphocyte distinguished tuberculous effusions from parapneumonic (p less than 0.001), nonspecific (p less than 0.001) and rheumatoid effusions (p less than 0.005), as well as from effusions caused by undefined connective tissue disease (p less than 0.001). Eosinophilia (more than 10%) of the pleural fluid was not present in any patient with proven tuberculosis and in only one patient with malignant effusion (malignant mesothelioma) but did occur in 12 of the 26 patients with nonspecific effusion. These results show that a great lymphocytic predominance is characteristic particularly of tuberculous but also of malignant pleural effusions, although this predominance cannot be regarded as disease-specific. Eosinophilia of the pleural fluid--usually a nonspecific sign--indicates nontuberculous, nonmalignant etiology.

In plain English

This prospective study from Finland asked whether counting white blood cells (leukocytes) in fluid that collects around the lungs (pleural effusion) helps show what caused the fluid. It included 140 consecutive patients whose fluid was sampled for diagnosis between 1976 and 1979. Twelve were excluded, leaving 128. Total leukocyte counts did not differ significantly between exudates of different causes. Lymphocytes made up more than 80% of cells in 47 of 55 patients with tuberculosis or malignant disease, but such counts were also found in many patients with other causes. Lymphocyte percentages in verified tuberculous effusions were significantly higher than in pneumonia-related, nonspecific and rheumatoid effusions, but did not differ significantly from malignant effusions. Eosinophilia (more than 10%) occurred in 26 patients (19%), including one with malignant mesothelioma. Only one of 23 verified tuberculous effusions contained any eosinophils (3.0%). Five patients had malignant mesothelioma, and none had a history of asbestos exposure. The authors concluded that the differential count helps indicate the cause of an effusion.

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: Prospective study of consecutive patients. Leukocyte counts were made at the first diagnostic puncture, and the cause of each effusion was determined retrospectively with at least 1 year of follow-up.
• Who was studied: 140 consecutive patients (99 men, 41 women) who had thoracentesis to diagnose a pleural effusion, examined between January 1, 1976 and December 31, 1979 at hospitals in Mjölbölsta and Helsinki, Finland. Twelve were excluded (7 with empyema, 4 with effusion from past pneumothorax therapy for tuberculosis, 1 after pulmectomy), leaving 128 patients. Of these, 86 had verified and 42 had unverified causes.
• Exposure: Asbestos exposure was not studied. The article notes that none of the 5 patients with malignant mesothelioma had a history of exposure to asbestos.
• Main results:
  • Total leukocyte counts were lower in transudates than in exudates. Among exudates of different causes, the counts showed no significant differences.
  • Lymphocytes made up more than 80% of leukocytes in 47 of the 55 patients with tuberculosis (verified or probable) or malignant disease. This included 18 of the 24 patients with malignant disease. Such counts were also found in many effusions of other causes.
  • The mean lymphocyte percentage in verified tuberculous effusions was significantly higher than in parapneumonic, nonspecific and rheumatoid effusions, and in effusions caused by undefined connective tissue disease.
  • The mean lymphocyte percentage in tuberculous effusions did not differ significantly from that in transudates or in effusions caused by malignant disease or systemic lupus erythematosus.
  • 26 patients (19%) had eosinophilic effusions (more than 10% eosinophils). Only one of these was a malignant effusion, and it was malignant mesothelioma.
  • Of the 23 verified tuberculous pleural effusions, only one contained eosinophils, at 3.0%.
  • In the 81 patients whose symptom duration could be estimated, lymphocytes tended to predominate when symptoms had lasted more than two weeks. The correlation between lymphocyte percentage and symptom duration was not statistically significant.
• The authors' conclusion: The authors concluded that the differential leukocyte count in pleural fluid is helpful in indicating the cause of an effusion. In their view, a considerable lymphocyte predominance is characteristic of, but not specific for, tuberculous and malignant effusions. They also concluded that eosinophilia suggests a cause that is neither tuberculous nor malignant, although the cause of such effusions often remains unknown.
• Limitations the authors state:
  • Large mononuclear cells were not separated into macrophages and mesothelial cells in this study.

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: Pleural Effusion, Thoracentesis, Exudate, Etiology, Mesothelioma.

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• Utility of hyaluronic acid in pleural fluid for differential diagnosis of pleural effusions: likelihood ratios for malignant mesothelioma — S. Atagi, M. Ogawara, et al. (1997)
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• Diagnostic usefulness of tumour marker levels in pleural effusions of malignant and benign origin — F. Kuralay, Z. Tokgöz, et al. (2000)
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