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Lymphocyte populations in tuberculous pleural effusions
M E San José1, L Valdés, M J Saavedra
1Servicio de Análisis Clínicos, Hospital de Conxo (Complejo Hospitalario Universitario de Santiago, Spain. csgabcsc@cesga.es
Insights
Activated T lymphocytes in pleural fluid are key indicators for diagnosing tuberculous pleuritis, outperforming peripheral blood analysis. This compartmentalization highlights the importance of local immune responses in tuberculosis diagnosis.
Area of Science:
- Immunology
- Pulmonology
- Infectious Diseases
Background:
- Systemic and local immune responses to mycobacterial antigens suggest lymphocyte compartmentalization in tuberculosis.
- Analyzing peripheral blood alone may inaccurately represent the immune status in pleural effusions.
- Understanding lymphocyte distribution is crucial for accurate diagnosis of pleural diseases.
Purpose of the Study:
- To investigate lymphocyte compartmentalization in patients with pleural effusions.
- To evaluate the diagnostic utility of specific lymphocyte subpopulations in pleural fluid versus peripheral blood for tuberculosis.
- To compare the efficiency of lymphocyte analysis with adenosine deaminase (ADA) determination.
Main Methods:
- Flow cytometry was used to analyze lymphocyte subpopulations (B, T, CD4+, CD8+, CD3+DR+) in pleural fluid and peripheral blood from 140 patients.
- Patients were categorized into six groups based on effusion etiology: tuberculous, paraneoplastic, metapneumonic empyematous, transudate, miscellaneous exudate, and unknown.
- Diagnostic efficiency, positive predictive value (PPV), and negative predictive value (NPV) were calculated for various markers and ratios.
Main Results:
- The CD3+DR+ (activated T lymphocyte) population in pleural fluid showed 84% diagnostic efficiency for tuberculosis.
- The pleural fluid/peripheral blood ratio of CD3+DR+ cells demonstrated 83% efficiency and significant differences across most etiological groups.
- Activated T lymphocytes were significantly higher in pleural fluid than peripheral blood in tuberculous pleuritis, correlating with ADA levels.
Conclusions:
- Lymphocyte compartmentalization is confirmed in tuberculous pleuritis, with a higher concentration of activated T lymphocytes in pleural fluid.
- Analysis of activated T lymphocytes (CD3+DR+) in pleural fluid offers significant diagnostic value for tuberculous pleuritis.
- Pleural fluid analysis, particularly of lymphocyte subpopulations and ADA, is superior to peripheral blood analysis for diagnosing tuberculous pleuritis.
Abstract:
Different systemic and local responses to mycobacterial antigens suggest an active compartmentalization of responsive lymphocytes to tubercular antigens. This fact, observed in pleuritic processes, raises doubts about the accuracy of information obtained in the study of cells taken solely from peripheral blood. For this reason we decided to study the concept of compartmentalization in 140 patients suffering from pleural effusions. Patients were classified into six groups according to the aetiology of the effusion: group I, tuberculous, n = 23; group II, paraneoplastic, n = 41; group III, metapneumonic empyematous, n = 5; group IV, transudate, n = 38; group V, miscellaneous exudate, n = 19; group VI, unknown aetiology, n = 14. In each group we studied the lymphocyte population by using flow cytometry with doubly fluorescent monoclonal antibodies: B [expressing human lymphocyte antigen (HLA)-DR on the surface], T (CD3+), CD4+ and CD8+, and the subpopulation of activated T lymphocytes (together expressing CD3 and HLA-DR on the surface) (CD3+DR+). The study of these subpopulations in peripheral blood did not yield valuable results, but the CD3+DR+ population in pleural fluid demonstrated a diagnostic efficiency of 84% [positive predictive value (PPV) 51%, negative predictive value (NPV) 96%] at a cut-off value of 80.4 cells/mm3. The CD3+DR+ pleural fluid/peripheral blood ratio demonstrated an efficiency of 83% (PPV 50%, NPV 96%), and showed a statistically significant difference (P < 0.02) with regard to all the diagnostic groups, with the exception of the paraneoplastic effusions. The lymphocytic subpopulations study confirms the concept of compartmentalization in tuberculous pleuritis, as shown by the greater number of activated T lymphocytes present in pleural fluid in comparison with peripheral blood in tuberculous pleuritis, a 98% efficiency of adenosine deaminase (ADA) determination in pleural fluid versus a 50% value in peripheral blood, predominance of helper cells (CD4+) in pleural fluid and suppressor cells (CD8+) in peripheral blood, a greater CD4+/CD8+ ratio in pleural fluid than in peripheral blood, and a significant correlation of ADA-CD3+DR+ in pleural fluid, which does not occur in peripheral blood.