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Vol. 56. Issue 7.
Pages 426-434 (July 2020)
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Vol. 56. Issue 7.
Pages 426-434 (July 2020)
Original Article
Identification of Pleural Response Patterns: A Cluster Analysis
Identificación de patrones de respuesta pleural: un análisis de conglomerados
Lucía Ferreiroa,b,
Corresponding author

Corresponding author.
, Óscar Lado-Baleatoc,d, María E. Toubesa, Juan Suárez-Anteloa, Antonio Pose-Reinoe, María E. San Joséf,b, José Manuel Álvarez-Dobañoa,b, Francisco J. González-Barcalaa,b, Jorge Ricoya, Francisco Gudec,d, Luis Valdésa,b
a Department of Pulmonology, University Clinical Hospital of Santiago, Santiago de Compostela, Spain
b Interdisciplinary Group of Research in Pulmonology, Health Research Institute of Santiago de Compostela (IDIS), Santiago de Compostela, Spain
c Department of Epidemiology, University Clinical Hospital of Santiago, Santiago de Compostela, Spain
d Research Group on Epidemiology of Common Diseases, Santiago de Compostela Health Research Institute (IDIS), Santiago de Compostela, Spain
e Department of Internal Medicine, University Clinical Hospital of Santiago, Santiago de Compostela, Spain
f Department of Clinical Laboratory Analysis, University Clinical Hospital of Santiago, Santiago de Compostela, Spain
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Figures (5)
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Tables (4)
Table 1. Etiology of pleural effusions and origin of metastatic pleural effusions.
Table 2. Demographic and clinical characteristics of patients.
Table 3. Classification of pleural effusions according to their etiology and the cluster they belong to.
Table 4. Analytical characteristics of malignant, uncomplicated parapneumonic pleural effusions and due to heart failure according to the cluster in which they were classified.
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Additional material (1)

Pleural effusion occurs as a response of the pleura to aggressions. The pleura reacts differently according to the type of injury. However, pleural reactions have not yet been characterized. The objective of this study was to identify homogeneous clusters of patients based on the analytical characteristics of their pleural fluid and identify pleural response patterns.


A prospective study was conducted of consecutive patients seen in our unit for pleural effusion. Principal component and cluster analyses were carried out to identify pleural response patterns based on a combination of pleural fluid biomarkers.


A total of 1613 patients were grouped into six clusters, namely: cluster 1 (10.5% of the cohort, primarily composed of patients with malignant pleural effusions); cluster 2 (17.4%, pleural effusions with inflammatory biomarkers); cluster 3 (16.1%, primarily composed of patients with infectious pleural effusions); cluster 4 (2.5%, a subcluster of cluster 3, superinfectious effusions); cluster 5 (23.4%, paucicellular pleural effusions); and cluster 6 (30.1%, miscellaneous). Significant differences were observed across clusters in terms of the analytical characteristics of PF (p<0.001 for all), age (p<0.001), and gender (p=0.016). A direct relationship was found between the type of cluster and the etiology of pleural effusion.


Pleural response is heterogeneous. The pleura may respond differently to the same etiology or similarly to different etiologies, which hinders diagnosis of pleural effusion.

Cluster analysis
Pleural effusion
Pleural fluid

El derrame pleural ocurre como una respuesta de la pleura a las agresiones. La pleura reacciona de manera diferente según el tipo de lesión. Sin embargo, las reacciones pleurales aún no se han clasificado. El objetivo de este estudio fue identificar grupos homogéneos de pacientes basados en las características analíticas de su líquido pleural e identificar patrones de respuesta pleural.


Se realizó un estudio prospectivo de pacientes consecutivos ingresados en nuestra unidad por presentar derrame pleural. Se llevaron a cabo análisis de componentes principales y análisis de conglomerados para identificar los patrones de respuesta pleural basados en las combinaciones de biomarcadores del líquido pleural.


Un total de 1.613 pacientes se agruparon en 6 grupos: conglomerado 1 (10,5% de la cohorte, compuesto principalmente por pacientes con derrames pleurales malignos); conglomerado 2 (17,4%, derrames pleurales con biomarcadores inflamatorios); conglomerado 3 (16,1%, compuesto principalmente por pacientes con derrames pleurales infecciosos); conglomerado 4 (2,5%, un subgrupo del conglomerado 3, derrames superinfecciosos); conglomerado 5 (23,4%, derrames pleurales paucicelulares), y el conglomerado 6 (30,1%, miscelánea). Se observaron diferencias significativas entre los grupos en las características analíticas del líquido pleural (p < 0,001 para todos), la edad (p < 0,001) y el género (p = 0,016). Se encontró una relación directa entre el tipo de conglomerado y la etiología del derrame pleural.


La respuesta pleural es heterogénea. La pleura puede responder de manera diferente a una misma etiología o de manera similar en diferentes etiologías, lo que dificulta el diagnóstico de derrame pleural.

Palabras clave:
Análisis de conglomerados
Derrame pleural
Líquido pleural


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