Efficacy of adenosine deaminase in the diagnosis of pleural effusions

Adenosine deaminase (ADA) activity was studied in 53 patients with pleural effusions. Patients with tuberculous pleural effusion (36) had significantly higher ADA activity (77.68 IU/L; P less than 0.001) in comparison to malignant (14.47 IU/L) and parapneumonic (28.65 IU/L) effusions. When tested with a reference limit of over 50.75 IU/L, the specificity of ADA activity was found to be 94.1 per cent. With a sensitivity of 100 per cent, low cost and easy performance pleural fluid ADA activity is proposed as a routine investigation for etiological diagnosis in pleural effusion.     

Discrimination of exudative pleural effusions based on multiple biological parameters.

Pleural effusion is a common complication of various diseases. Conventional methods are not always capable of establishing the cause of pleural effusion, so alternative tests are needed. The aim of this study was to explore means of discriminating between different pleural effusion groups, malignant, parapneumonic and tuberculous, based on the combined function of seven biological markers. Adenosine deaminase (ADA), interferon-gamma, C-reactive protein (CRP), carcinoembryonic antigen, interleukin-6, tumour necrosis factor-alpha and vascular endothelial growth factor concentration levels were measured in pleural fluid from 45 patients with malignant, 15 with parapneumonic and 12 with tuberculous pleural effusion. Receiver operating characteristic curve analysis, multinomial logit modelling and canonical variate analysis were applied to discriminate the pleural effusion groups. The three groups could be discriminated successfully using the measured markers. The most important parameters for discrimination were ADA and CRP concentration levels. An individual with an ADA concentration level of >45 U.L(-1) and a CRP concentration of <4 mg.dL(-1) was more likely to belong to the tuberculous pleural effusion group, whereas one with an ADA concentration level of <40 U.L(-1) and a CRP concentration of >6 mg.dL(-1) was more likely to belong to the parapneumonic pleural effusion group, and one with a CRP concentration of <4 mg.dL(-1) to the malignant pleural effusion group. The combination of adenosine deaminase and C-reactive protein levels might be sufficient for discriminating between the three different groups of exudative pleural effusion: malignant, tuberculous and parapneumonic.     

Adenosine deaminase 2 in the diagnosis of tuberculous pleuritis

PURPOSE: We examined the usefulness of adenosine deaminase 2 (ADA2) in the diagnosis of tuberculous pleuritis. SUBJECTS: A hundred cases, 78 male and 22 female, with pleural effusion were examined. With regard to pleural effusion, 18 cases were transudate and 82 cases (9 tuberculous pleuritis, 27 lung cancer, 8 mesothelioma, 5 malignant diseases except lung cancer and mesothelioma, 5 benign asbestos pleurisy, 10 empyema, 10 parapneumonic effusion, one SLE, one parasitic infection, and 6 undetermined etiology) were exudates. The last 6 cases with unknown origin were excluded in this study. RESULTS: Pleural adenosine deaminase (ADA) was 90.4 +/- 22.4 U/l (mean +/- SD) and pleural ADA2 was 80.4 +/- 21.9 U/l in tuberculous pleuritis, both were significantly higher than those in non-tuberculous exudates (p < 0.001). In the diagnosis of tuberculous pleuritis, pleural ADA showed 100% sensitivity and 88% specificity, whereas pleural ADA2 showed 100% sensitivity and 91% specificity. CONCLUSION: Pleural ADA2 is useful in the diagnosis of tuberculous pleuritis, which has similar sensitivity and a little better specificity compared with pleural ADA.     

Adenosine deaminase activity in pleural fluid--a diagnostic test of tuberculous pleural effusion.

Adenosine deaminase (ADA) activity in pleural fluids was studied in 47 patients with pleural effusion of different etiology. Patients were divided into two groups: Group I - Tuberculous pleural effusion (21 patients): Group II - Non tuberculous effusion (26 patients) and these included malignant pleural effusion (9 cases), synpneumonic pleural effusion (9 cases) and transudative pleural effusion (8 cases). The mean ADA activity was 64.67 IU/L +/- 21.68 in group I and 6.99 +/- 3.69 in Group II. Increased mean pleural fluid ADA activity in tuberculous pleural effusion was highly significant (p < 0.001) when compared with pleural effusion of non-tuberculous etiology. Based on lowest value of ADA activity found in tuberculous pleural effusion (30 IU/L), the test has a sensitivity and specificity of 1.     

Diagnostic value of adenosine deaminase in nontuberculous lymphocytic pleural effusions.

Adenosine deaminase (ADA) can aid in the diagnosis of tuberculous pleural effusions, but false-positive findings from lymphocytic effusions have been reported. The purpose of this study is to assess the ADA levels in nontuberculous lymphocytic pleural effusions (lymphocyte count > 50%) of different aetiologies. Altogether, 410 nontuberculous lymphocytic pleural fluid samples were consecutively selected. These included malignant effusions (n = 221), idiopathic effusions (n = 76), parapneumonic effusions (n = 35), postcoronary artery bypass graft surgery effusions (n = 6), miscellaneous exudative effusions (n = 21) and transudative effusions (n = 51). The ADA level reached the diagnostic cut-off for tuberculosis (40 U x L(-1)) in seven of the 410 cases (1.71%). The negative predictive value of ADA for the diagnosis of pleural tuberculosis was 99% (403 of 407 cases) in the group of lymphocytic pleural effusions. In five of these seven patients ADA1 and ADA2 were measured, and in all these cases (100%) ADA1/ADA(p) correctly classified these lymphocytic effusions as nontuberculous (ratio < 0.42). This prospective study provides additional evidence that adenosine deaminase levels in nontuberculous lymphocytic pleural effusions seldom exceed the cut-off set for tuberculous effusions. The pleural fluid adenosine deaminase levels were significantly higher in different types of exudative effusions than in transudates. An adenosine deaminase level < 40 IU x L(-1) virtually excluded a diagnosis of tuberculosis in lymphocytic pleural effusions. Adenosine deaminase1/adenosine deaminase(p) correctly classified all nontuberculous lymphocytic pleural effusions with high adenosine deaminase levels.     

干扰素γ、白细胞介素12及腺苷脱氨酶同工酶对结核性胸腔积液的诊断价值

目的　研究胸腔积液中干扰素γ(IFN γ)和白细胞介素 12 (IL 12 )的浓度及腺苷脱氨酶同工酶 (ADA2 )的活性三者在结核性胸腔积液诊断中的临床价值。方法　以 2 0 0 2年 3月～ 2 0 0 3年2月期间在北京大学人民医院、北京胸科医院、北京结核病胸部肿瘤研究所等医院的未经治疗的胸腔积液患者为研究对象 ,其中结核性胸腔积液 14 1例、恶性胸腔积液 4 9例。应用酶速率法检测胸腔积液标本中腺苷脱氨酶 (ADA)、ADA2 的活性 ,酶联免疫吸附测定 (ELISA)检测IFN γ和IL 12的浓度。比较两组胸腔积液中ADA和ADA2 活性 ,以及IFN γ和IL 12浓度之间的区别。结果　 (1)结核性胸腔积液组ADA、ADA2 活性分别为 (5 1 6± 10 9)U/L和 (4 7 9± 6 9)U/L ,恶性胸腔积液组ADA、ADA2 活性分别为 (2 0 4± 4 4 )U/L、(13 2± 3 2 )U/L ,结核性胸腔积液组的ADA、ADA2 活性显著高于恶性胸腔积液组 (P <0 0 1)。结核性胸腔积液组IFN γ和IL 12浓度分别为 (112 1± 4 5 8)ng/L及 (10 4 3± 32 3)ng/L ,恶性胸腔积液组IFN γ和IL 12浓度分别为 (2 4 8± 5 9)ng/L和 (6 1 8±10 8)ng/L ,结核性胸腔积液组的IFN γ和IL 12浓度水平显著高于恶性胸腔积液组 (P <0 0 1,0 0 5 ) ;(2 )ROC曲线分析结果 ,IFN γ以 6 1 7ng/L为诊     

腺苷脱氨酶诊断结核性胸膜炎价值的再评价

目的 探讨胸腔积液和血清中腺苷脱氨酶(ADA)对鉴别结核性胸膜炎及恶性胸腔积液的临床价值.方法 回顾性分析91例经内科胸腔镜胸膜活检病理确诊为结核性胸腔积液(结核组49例)和恶性胸腔积液(恶性组42例)患者的胸腔积液及血清中ADA活性,应用受试者工作曲线(ROC曲线)确定结核性胸膜炎患者胸腔积液ADA的最佳临界值.结果 结核组胸腔积液ADA活性和胸腔积液ADA与血清ADA比值分别为(46±26)U/L和4.1±4.0,明显高于恶性组的(16±8)U/L和1.7±1.2,差异均有统计学意义(t值分别为7.383和3.852,均P＜0.01),结核组和恶性组的血清ADA活性分别为(13±5)U/L和(12±6)U/L,差异无统计学意义(t=1.582,P＞0.05).应用ROC曲线确定胸腔积液ADA诊断结核性胸膜炎的最佳临界值为28.7 U/L,灵敏度为75.5%,特异度为95.2%.结论 胸腔积液ADA活性可以作为鉴别结核性和恶性胸腔积液的重要指标,对结核性胸膜炎有较高的临床诊断价值,而血清ADA活性对鉴别两者无临床意义.     

66例大量胸腔积液病因及诊断分析

目的分析大量胸腔积液的病因和诊断方法。方法回顾性分析66例大量胸腔积液住院患者的临床资料。结果 66例大量胸腔积液病因的前5位依次为恶性肿瘤（56.1%）,结核（24.2%）,肺炎旁积液和脓胸（6.1%）,肝硬化（4.5%）,外伤（3.0%）。大量良性胸腔积液以40岁以下患者为主;恶性胸腔积液以60岁以上患者居多。66例大量胸腔积液癌胚抗原水平均为恶性组高于良性组（P〈0.05）,腺苷脱氨酶水平均为恶性组低于良性组（P〈0.05）。结论大量胸腔积液主要病因是恶性肿瘤和结核,恶性肿瘤多见于60岁以上患者,结核病以40岁以下患者居多。胸腔积液癌胚抗原及腺苷脱氨酶含量鉴别良恶性胸腔积液有重要的价值。     

Differential diagnosis of tuberculous pleurisy by measurement of cytokine concentrations in pleural effusion

Study objective: Measurement of cytokine concentration in serum and pleural effusion may be useful in the differential diagnosis of tuberculous pleurisy.Patients and methods: We compared the biochemical properties and concentrations of cytokines in serum and pleural effusion samples of 18 patients with tuberculous pleurisy, 7 patients with parapneumonic pleurisy, and 25 patients with malignant pleurisy.Results: A high value of adenosine deaminase (ADA) was observed in pleural effusion of patients with tuberculosis. The serum concentrations of interleukin (IL)-1-beta, IL-2, interferon (IFN)-gamma and tumor necrosis factor (TNF)-alpha were similar among the three groups. However, the concentration of IFN-gamma in pleural effusion was high in tuberculous patients, and that of TNF-alpha was high in tuberculous and parapneumonic pleural fluid, but both cytokines were low in malignant pleural fluid. The sensitivity, specificity and accuracy of IFN-gamma in the diagnosis of tuberculous pleurisy were 94%, 100% and 98%, respectively. Similarly, those of TNF-alpha for the diagnosis of infectious pleurisy including tuberculous and parapneumonic pleurisy were 88%, 80% and 84%, respectively.Conclusions: Our results indicate that simultaneous measurement of IFN-gamma and TNF-alpha in pleural effusion is a useful diagnostic tool for differentiating tuberculous pleurisy from parapneumonic and malignant pleurisy.     

ADA、IFNγ-、sIL-2R检测在鉴别结核性和癌性胸水中的价值

目的研究腺苷脱氨酶（ADA）、γ干扰素（IFN-γ）、可溶性白介素2受体（sIL-2R）对结核性胸水和癌性胸水鉴别诊断的价值。方法采用酶法和ELISA方法检测47例结核性胸水患者和47例癌性胸水患者胸水中ADA活性和IFNγ-、sIL-2R水平。结果结核性胸水组的ADA（72.3±21.7 U/L）、IFN-γ（481.3±257.1 pg/m l）和sIL-2R（611.0±184.4 pmol/L）都显著高于癌性胸水组（P〈0.01）;当以ADA≥46.8 U/L、IFNγ-≥209.0 pg/m l和sIL-2R≥491.5 pmol/L为临界值,三项指标对结核性胸水的敏感度分别为93.6%,87.2%,70.2%;特异度分别为91.5%,91.5%,78.7%。结论胸水中ADA、IFN-γ和sIL-2R对结核性胸水和癌性胸水的鉴别诊断都有较高的临床价值。     

Transforming growth factor beta-1 level in pleural effusion

OBJECTIVE: Transforming growth factor-beta1 is an important immunomodulator. The diagnostic role of TGF-beta1 has not been systematically investigated in pleural effusion. METHODOLOGY: A prospective clinical study of 45 patients (23 men, 22 women; mean age 49 +/- 21 years) with pleural effusion was performed. Of these patients, 19 had malignant pleural effusion, 14 had tuberculous pleural effusion, seven had empyema/parapneumonic pleural effusion, and five had transudative pleural effusion due to congestive heart failure. The concentrations of TGF-beta1 were measured by ELISA in all pleural fluid samples and in serum samples only from patients with malignant and tuberculous pleural effusions. RESULTS: The median TGF-beta1 levels of malignant, tuberculous and empyema/parapneumonic pleural effusions were 7.25 ng/mL, 7.81 ng/mL, and 9.75 ng/mL, respectively. There was no significant difference between them. The median TGF-beta1 level was 5.62 ng/mL in the transudate pleural effusion group and it was significantly lower than that in the empyema/parapneumonic group (P < 0.05). The pleural fluid TGF-beta1 levels did not correlate with cell profiles of the pleural fluid. The median serum TGF-beta1 levels in malignant and tuberculous pleural effusion groups were 7.38 ng/mL and 7.38 ng/mL, respectively. There was no significant difference between the levels of TGF-beta1 in paired samples of serum and pleural fluid. CONCLUSIONS: This study shows that TGF-beta1 concentrations in exudative pleural effusions are higher than those in transudative effusions secondary to congestive heart failure but TGF-beta1 concentrations do not assist in differentiating exudative effusions.     

结核性与癌性胸腔积液的实验室检测比较研究

目的比较研究实验室检测腺苷脱氨酶(ADA)、乳酸脱氢酶(LDH)、癌胚抗原(CEA)、蛋白(TP)、葡萄糖(GLU)等多项指标对结核性与癌性胸腔积液的鉴别诊断价值。方法对151例明确诊断为结核性或癌性胸腔积液分别测定胸水ADA、LDH、CEA、TP、GLU和血清TP,并进行统计分析。结果结核性胸腔积液中ADA、LDH、TP含量都明显高于癌性胸腔积液,其中胸水ADA以28U/L作为诊断结核性胸水的临界值则其敏感性和特异性均极高,结核性胸水中GLU含量则低于癌性胸水,癌性胸水CEA的阳性率高达76.0%,而结核性胸水CEA均阴性。结论联合检测胸水ADA、LDH、CEA、TP和GLU可以作为结核性与癌性胸腔积液的诊断和鉴别诊断依据,其中ADA28U/L可以考虑作为结核性胸腔积液的单独诊断依据。     

腺甘脱氨酶、肿瘤坏死因子α、白细胞介素对结核性与恶性胸水鉴别诊断的价值

目的探讨胸水中腺甘脱氨酶（ADA）、肿瘤坏死因子-α[（TNF—α）、白细胞介素-2（IL-2）和IL-6水平对结核性与恶性胸水鉴别诊断的价值。方法采用酶法和化学发光法对49例结核性胸水与43例恶性胸水患者ADA、IL-2、IL-6、TNF-α水平进行检测。结果结核性胸水组患者胸水中ADA、IL-5、TNF-α含量明显高于恶性胸水组（P〈0．01）,而胸水IL-2含量在两组患者间比较无统计学意义（P〉0．05）。结论检测胸水中ADA、IL-5、TNF-α的水平对鉴别结核性与恶性胸水有较高的临床价值。     

Pleural SC5b-9 in differential diagnosis of tuberculous, malignant, and other effusions.

A monoclonal antibody against soluble phase-terminal complement complex (SC5b-9) was used to try to differentiate pleural effusions of tuberculous vs malignant and other origin. Effusions of tuberculous origin showed a significantly higher SC5b-9 level than did plasma, suggesting activation of complement in the pleural space. All 26 patients with tuberculous effusions showed SC5b-9 levels in pleural fluid exceeding 2.0 mg/L, while 20 with malignant effusions had levels less than 2.0 mg/L. However, rheumatoid, some parapneumonic, and treated malignant effusions showed SC5b-9 levels above 2.0 mg/L. Considering a value exceeding 2.0 mg/L, the specificity and sensitivity of the SC5b-9 estimation in tuberculosis were 0.74 and 1.0, respectively. The mean values for C4d and Bb fragments of complement were significantly (p < 0.05) higher in the tuberculous than in the malignant effusions. However, the values for Bb in 16 (62 percent) of the 26 patients with tuberculous or malignant effusions were in the same range. The activity of adenosine deaminase (ADA) was higher in the tuberculous than in the malignant effusions. While 18 of 26 patients with tuberculous effusions showed an ADA value exceeding 50 mU/ml, the estimated cutoff point (sensitivity = 0.69), 35 of the 36 nontuberculous effusions showed a true negative value (specificity = 0.97). A correlation between ADA and SC5b-9 values was observed in pleural effusions. These observations suggest that the estimation of SC5b-9 in pleural fluid presents a new approach to differentiating tuberculous vs malignant effusions.     

血管内皮细胞生长因子C与腺苷脱氨酶联合检测在胸腔积液鉴别诊断中的意义

目的 了解血管内皮细胞生长因子C(VEGF-C)及腺苷脱氨酶(ADA)在不同原因胸腔积液中的表达,并探讨通过比值构建联合诊断对胸腔积液鉴别诊断的作用.方法 选择143例临床确诊的胸腔积液患者(恶性胸腔积液40例,结核性胸膜炎45例,其他类型58例),采用双抗夹心ELISA法检测胸水VEGF-C,采用速率法检测胸水ADA,计算VEGF-C/ADA比值,比较不同类型胸腔积液患者中上述诊断指标的变化,并计算它们的敏感度、特异度和准确度.结果 恶性胸腔积液中VEGF-C浓度高于结核性胸腔积液及类肺炎性等其他类型胸腔积液,(286.32±102.65)ng/L vs(133.46±39.83)ng/L,(140.14±44.62)ng/L,P<0.05.结核性胸腔积液中ADA浓度高于恶性胸腔积液及其他类型胸腔积液,(78.6±36.3)IU/L vs(23.4±11.2)IU/L,(26.1±10.5)IU/L,P<0.05.VEGF-C/ADA≥8对恶性胸腔积液诊断的敏感度为87.5%,特异度为81.4%;VEGF-C/ADA≤3对结核性胸腔积液诊断的敏感度为84.4%,特异度为86.4%.结论 VEGF-C与ADA浓度比值对胸腔积液的鉴别诊断具有较好的临床价值.     

Adenosine Deaminase in the Diagnosis of Pleural Effusions

ABSTRACT The activity of adenosine deaminase (ADA) was determined in serum and pleural fluid of 90 patients with pleural effusions of various aetiology. Tuberculous pleural effusions, empyemas and rheumatoid pleural effusions demonstrated significantly higher activities of ADA than parapneumonic, nonspecific and malignant pleural effusions and effusions in systemic lupus erythematosus and congestive heart failure. In tuberculosis, empyema and rheumatoid arthritis ADA activity was significantly higher in pleural fluid than in serum, indicating a local synthesis of ADA by cells within the pleural cavity in these diseases.     

Tumour necrosis factor-alpha in comparison to adenosine deaminase in tuberculous pleuritis

BACKGROUND: Adenosine deaminase (ADA) is already used for the differential diagnosis of tuberculosis pleurisy. Tumour necrosis factor-alpha (TNF) is another marker which has been investigated for this purpose. OBJECTIVE: We evaluated the diagnostic value of pleural fluid and serum TNF concentrations in tuberculous pleuritis and compared them to ADA. METHODS: Sixty-two patients (24 tuberculous pleuritis, 38 non-tuberculous pleuritis) with exudative pleurisy were included. Serum and pleural fluid TNF concentrations were determined in all patients and ADA activity in 54 patients. Pleural fluid TNF concentrations and pleural fluid/serum TNF were compared to pleural fluid ADA activity and pleural fluid/serum ADA. RESULTS: When the tuberculous and non-tuberculous groups were compared, pleural fluid TNF concentrations (65.4 +/- 136.9 pg/ml vs. 54.5 +/- 144.2 pg/ml, respectively; p < 0.001), pleural fluid ADA activity (74.2 +/- 33.3 U/l vs. 23 +/- 16.3 U/l; p < 0.0001), pleural fluid/serum TNF (2.55 +/- 5.23 vs. 0.26 +/- 0.2; p < 0.001) and pleural fluid/serum ADA (4.58 +/- 8.14 vs. 1.15 +/- 0.7; p < 0.0001) were significantly higher in the tuberculous group. When cut-off points were assessed, 8 pg/ml and 40 U/l were found for pleural fluid TNF concentrations and pleural fluid ADA activity, respectively. Sensitivity, specificity, area under the curve were 87.5%, 76.3%, 0.772 for pleural fluid TNF concentrations and 90.9%, 89.5%, 0.952 for pleural fluid ADA activity, respectively; the difference between these areas under the curves was significant (p < 0.05). CONCLUSIONS: Pleural fluid TNF levels and pleural fluid/serum TNF were higher in tuberculous effusions than in other exudates, but their diagnostic value appears to be poorer than that of ADA.     

降钙素原与CA125联合检测对结核性胸腔积液的诊断价值

目的探讨联合检测血清和胸腔积液降钙素原(PCT)、CA125对结核性胸腔积液的诊断价值。方法 30例结核性胸腔积液、20例肺炎旁积液、30例恶性胸腔积液,采用化学发光法测定血浆和胸腔积液中的PCT水平,快速发光免疫分析测定CA125的水平。结果结核组、肺炎组血清PCT水平差异无统计学意义(P>0.05),结核组和肺炎组胸腔积液中PCT的表达均较对照组明显升高(均P<0.05)。结核组和恶性组血清及胸腔积液中CA125水平较肺炎组显著升高(P<0.01)。结论联合检测血清及胸腔积液中PCT与CA125水平可提高结核性胸腔积液诊断的敏感性和特异性。     

Tuberculous effusion: ADA activity correlates with CD4+ cell numbers in the fluid and the pleura

BACKGROUND: Adenosine deaminase (ADA) is a commonly used marker in the diagnosis of tuberculous effusion and there is evidence that its production is linked to T cells and monocytes. Data on the correlation between ADA and T cells or macrophages in tuberculous effusions are conflicting. Furthermore, no studies have examined a possible correlation between pleural tissue infiltration and ADA. OBJECTIVES: We undertook this study to examine cell subsets in the fluid and the pleura in tuberculous effusion and their correlation to ADA. The use of cell subsets as a marker in the differential diagnosis was also examined. METHODS: Pleural fluid from 36 patients with tuberculous and 34 patients with malignant effusion as well as pleural tissue biopsies from 16 patients with tuberculous pleurisy were examined. The APAAP and the avidin-biotin complex immunocytochemical methods were used to examine CD4+ T cells and macrophages (CD68+), while ADA activity was measured by the Giusti colorimetric method. RESULTS: Our results showed that, in pleural fluid, CD4+ cells and ADA were significantly higher in tuberculous compared to malignant effusion (p<0.001 for all measurements). In pleural tissue biopsies, macrophages were the predominant cells but CD4+ T cells were also abundant. A significant correlation was found between ADA and CD4+ numbers in pleural fluid and tissue (r=0.45, p<0.01; r=0.75, p<0.001, respectively). ADA had high sensitivity and specificity for differential diagnosis while cell subsets did not. CONCLUSIONS: These results indicate that ADA activity correlates to CD4+ T cell infiltration in the pleura and the fluid. Moreover, ADA but no cell subsets may be used as markers of tuberculous effusion.     

Diagnostic value of interleukin-1alpha, interleukin-6, and tumor necrosis factor in pleural effusions

STUDY OBJECTIVES: Interleukin (IL)-1alpha, IL-6, and tumor necrosis factor (TNF)-alpha were measured in pleural fluid from 57 patients with pleural effusion in order to evaluate the diagnostic utility of these cytokines. We studied 20 patients with malignant pleural effusion, 11 patients with parapneumonic pleural effusion, 9 patients with tuberculous pleural effusion, and 17 patients with transudative pleural effusion. Cytokines were measured by radioimmunoassay. SETTING: University tertiary hospital. RESULTS: The mean values of the three cytokines measured in pleural fluid or in serum were significantly higher in patients with exudates than with transudates (p < 0.05). The ratio of IL-6 in pleural fluid to serum was significantly higher in exudates than in transudates (p < 0.05). The level of IL-6 in pleural fluid was significantly higher in tuberculous than malignant (p < 0.007) or parapneumonic pleural effusions (p < 0.04). No significant difference between the three types of exudates was found in pleural fluid levels of IL-1alpha or TNF-alpha. CONCLUSIONS: Serum levels of IL-1alpha, TNF-alpha, and in particular IL-6 can distinguish exudates from transudates, while pleural fluid IL-6 levels could be useful as an additional marker in the differential diagnosis of tuberculous, malignant, and parapneumonic exudates. Finally, our results suggest that there is local cytokine production in exudative pleural effusions.