Chemical and immunological features of pleural effusions: comparison between rheumatoid arthritis and other diseases

Anatomy and pathophysiology of the pleura and pleural space

Pleural effusions are most often secondary to an underlying condition and may be the first sign of the underlying pathologic condition. The balance between the hydrostatic and oncotic forces dictates pleural fluid homeostasis. The parietal pleura has a more significant role in pleural fluid homeostasis. Its vessels are closer to the pleural space compared with its visceral counterpart; it contains lymphatic stomata, absent on visceral pleura, which are responsible for a bulk clearance of fluid. The diagnosis and successful treatment of pleural effusions requires a mixture of imaging techniques and pleural fluid analysis.

A systematic approach to the investigation and diagnosis of a unilateral pleural effusion

Fluid in the pleural space is a common sequela of a wide range of diseases which may be pulmonary, pleural or extrapulmonary. As the differential diagnosis is wide, a systematic approach to investigation and diagnosis is recommended. This review highlights the important features and recommendations for the investigation of a unilateral pleural effusion, a common condition encountered by the general physician. The aim of this study was to assist with a speedy diagnosis of the underlying pathology, using appropriate investigative techniques, while minimising the use of invasive procedures.

The value of pleural fluid analysis

Pleural fluid analysis in isolation may have clinical value. To have the greatest diagnostic impact, the clinician must formulate a prethoracentesis diagnosis based on the clinical presentation, blood tests, and radiographic imaging. With this approach, a definitive or confident clinical diagnosis can be expected in up to 95% of patients. The information in this report should allow the clinician to achieve this goal.

Collagen Vascular Diseases and Disorders of Connective Tissue

The collagen vascular diseases, also referred to as connective tissue diseases, are a diverse group of systemic inflammatory disorders thought to be immunologically mediated. The concept of collagen vascular disease began to take shape in the 1930s, when it was recognized that rheumatic fever and rheumatoid arthritis can affect connective tissues throughout the body.1,2 During the following decade, as conditions such as systemic lupus erythematosus (SLE) and scleroderma came to be viewed as systemic diseases of connective tissue, the terms diffuse connective disease and diffuse collagen disease were proposed.3,4 During the same period, the designation of diffuse vascular disease was proposed for diseases such as scleroderma, polymyositis, SLE, and polyarteritis nodosa, which featured widespread vascular involvement.5 With the realization that many of these entities can exhibit both systemic connective tissue manifestations and vascular abnormalities, the unifying designation of collagen vascular disease was introduced.6

Pleural effusion associated with rheumatoid arthritis: what cell predominance to anticipate?

Pleural involvement is the most frequent manifestation of rheumatoid arthritis (RA) in the chest. We report here two patients who presented with large exudative pleural effusions and subsequently developed sero-positive RA. In both cases, the differential cell count of the pleural effusion suggested empyema. A literature review identified that RA-associated pleural effusion afflicts more men than women and 95% of the patients have high titers of rheumatoid factor (RF). In 46% of cases, RA-associated pleural effusion is diagnosed in close temporal relationship with the diagnosis of RA. The effusion is an exudate and is characterized by low pH and glucose level, and high lactic dehydrogenase (LDH) and cell count. At diagnosis there is a tendency for predominant neutrophils to occur consistent with an empyema and 7-11 days later, the cells in the pleural effusion are replaced by lymphocytes. Pleural effusion with predominant eosinophilia is rare. RA patients with acidic effusion and low glucose content with neutrophils predominance should be treated with thoracic drainage and antibiotics until an infection is ruled out. The histo-pathologic findings in pleural fluid of tadpole cells and multinucleated giant cells and the replacement of the mesothelial cells on the parietal pleural surface with a palisade of macrophage derived cells are described as pathogonomic for RA. Treatment with systemic steroids and intra-pleural steroids are effective in most cases.

Rheumatoid Pleural Effusion

OBJECTIVES

To describe the clinical and laboratory features of rheumatoid pleural effusion (RPE) and the diagnostic and therapeutic approaches to this condition.

METHODS

The review is based on a MEDLINE (PubMed) search of the English literature from 1964 to 2005, using the keywords "rheumatoid arthritis" (RA), "pulmonary complication", "pleural effusion", and "empyema".

RESULTS

Pleural effusion is common in middle-aged men with RA and positive rheumatoid factor (RF). It has features of an exudate and a high RF titer. Underlying lung pathology is common. Generally RPE is small and resolves spontaneously but symptomatic RPE may require thoracocentesis. Rarely, RPE has features of a sterile empyematous exudate with high lipids and lactate dehydrogenase, and very low glucose and pH levels. This type of effusion eventually leads to fibrothorax and lung restriction. Superimposed infective empyema often complicates RPE. Oral, parenteral, and intrapleural corticosteroids, pleurodesis and decortication, have been used for the treatment of sterile RPE. Infected empyema is treated with drainage and antibiotics.

CONCLUSIONS

RPE may evolve into a sterile empyematous exudate with the development of fibrothorax. Symptomatic effusions or suspicion of other causes of exudate (infection, malignancy) require thoracocentesis. The "rheumatoid" nature of the pleural exudate in patients without arthritis mandates a pleural biopsy to exclude tuberculosis or malignancy. The optimal therapy of RPE has yet to be established. The role of cytokines in the course of RPE and the possible usefulness of cytokine blockade in the treatment of this RA complication require further evaluation.

Pleural effusion

Pleural disease remains a commonly encountered clinical problem for both general physicians and chest specialists. This review focuses on the investigation of undiagnosed pleural effusions and the management of malignant and parapneumonic effusions. New developments in this area are also discussed at the end of the review. It aims to be evidence based together with some practical suggestions for practising clinicians.

Rheumatoid Pleural Effusion in the Absence of Arthritic Disease

Rheumatoid pleural effusion is an unusual complication of rheumatoid disease that typically presents subsequent to other more common manifestations of rheumatoid illness. The case of a 72-year-old woman with a rheumatoid pleural effusion is discussed. The patient presented with dyspnea, but without any history of rheumatoid arthritis. The patient was treated by thoracentesis, followed by video-thoracoscopy and pulmonary decortication. Postoperatively, the patient's effusion partially reaccumulated. Steroid therapy resulted in prompt and permanent resolution of the effusion. The patient remains asymptomatic 1 year after her presentation. The biochemical, serologic, and cytologic characteristics of rheumatoid effusions are reviewed.

Cavitary Necrobiotic Nodule Imitating Malignant Lung Disease in a Patient Without Articular Manifestations of Rheumatoid Arthritis

Pulmonary involvement is a serious complication of rheumatoid arthritis (RA) and may be seen as airway disease, rheumatoid nodules, interstitial lung disease, and pleurisy. However, cavitary rheumatoid nodules without articular manifestations are rare. We describe a male patient presenting with pleurisy and multiple rheumatoid necrobiotic nodules in the absence of arthritis or subcutaneous nodules. One of the nodules was quite large (5 x 8 cm in diameter) and cavitary, imitating bronchial carcinoma radiologically and bronchoscopically. Definite histopathologic diagnosis was obtained by open lung biopsy. The patient was given methylprednisolone and methotrexate, and significant regression was observed in clinical and radiologic findings. He has been followed for 14 months with no articular manifestations yet, receiving 4 mg/d methylprednisolone and 20 mg/wk methotrexate. The diagnosis of rheumatoid pulmonary involvement without articular manifestations can be difficult. Rheumatoid nodules may imitate bronchial carcinoma, or bronchial carcinoma may coexist in RA patients. Open lung biopsy may be necessary for differential diagnosis of pulmonary lesions in RA.

Complement components and their activation products in pleural fluid

STUDY OBJECTIVES

The aim of this study was to determine the role of complement components in pleural effusion measured with novel markers of complement activation, to assess which pathway of activation is predominant in different diseases, and to find out whether the analysis of complement components and their activation products could help in diagnostic procedure differentiating the etiologies of pleural effusion.

PATIENTS

The study population consisted of 71 patients who had pleural effusion secondary to tuberculosis (n=23), rheumatic disease (n=10), or malignancy (n=38).

MEASUREMENTS

Complement components and their activation products, including the soluble terminal complex SC5b-9, were measured in plasma and pleural fluid.

RESULTS

In all patients with rheumatic pleurisy, pleural fluid SC5b-9 was higher than 2 AU/mL and in all patients with malignant pleural fluid it was lower than 2 AU/mL. The mean level of SC5b-9 in rheumatic pleural effusion was also significantly higher than in tuberculosis. In addition, the concentrations of pleural fluid C3 and C4 were significantly lower and the ratio C4d/C4 was significantly higher in rheumatic compared with tuberculous or malignant pleurisy. In plasma, both SC5b-9 and C1s-C1r-C1INH-complexes were significantly higher in rheumatic subjects than in other patients. In stepwise multinominal logistic regression analyses, the most significant predictors for rheumatic pleural fluid were high pleural fluid SC5b-9 and low C4.

CONCLUSIONS

These observations indicate that the complement cascade is activated through both the classic and the alternative pathways in rheumatic pleurisy. Determinations of SC5b-9 and C4d/C4 in pleural fluid were the best variables differentiating rheumatic, tuberculous, and malignant effusions.

[Pleural effusion as initial presentation of rheumatoid arthritis. Cytological diagnosis]

A 24-year-old woman with an unremarkable history presented with a large right-sided pleural effusion. Analysis of the pleural fluid showed a sterile exudate with a low sugar level. Complementary analyses were unable to pinpoint the etiology. The effusion was drained and the patient was released with no specific diagnosis. Nine months later the effusion recurred and the initial laboratory analyses were the same. Pleural fluid cytology revealed the presence of an amorphous necrotic background and non-small cells with multiple nuclei, two signs that constitute part of the pathognomonic triad of rheumatoid pleural effusions, the third characteristic benign fusiform histocytes. The biochemical characteristics of the pleural fluid thus suggested rheumatoid pleural effusion, and cytology confirmed the diagnosis. Corticoid therapy effected spectacular recovery, but when the dose was reduced, rheumatoid symptoms presented in the joints. Rheumatoid arthritis should be considered as a possible explanation for unexplained pleural effusion. Cytology must be used for diagnosis.

Postcardiac injury syndrome. An immunologic pleural fluid analysis

The postcardiac injury syndrome (PCIS) is characterized by inflammation of the pericardium, pleura, and pulmonary parenchyma following a variety of cardiac injuries. Although it has been clinically recognized for decades, confirmation of the syndrome has been problematic owing to lack of a sufficiently diagnostic test. Previously, we have reported pleural fluid characteristics which help to exclude other diagnoses that may mimic the syndrome. We describe the first immunologic assessment, including antimyocardial antibody testing, of pleural fluid from a patient with PCIS which supports a local immunologic mechanism in the pathogenesis of the syndrome. These results support the important role of pleural fluid analysis in the diagnosis of PCIS.

Anion gap in turpentine-induced pleural effusions. Correlation with pH and protein level

Since the pleural fluid proteins and lactate are unmeasured anions, the pleural fluid anion gap (Na+K-Cl-total CO2) should vary with the protein level and should be high in acidic effusions (which have high lactate levels). The anion gap is also convenient and inexpensive to measure, and less subject to artifact than the pH measurement. To test the hypothesis that the anion gap correlates with the pH, protein level, and other traditional pleural fluid measurements, we used a well-described model of turpentine-induced effusions in nine New Zealand white rabbits. Nonacidic exudative effusions were induced by an intrapleural injection of turpentine; acidic exudative effusions were induced by a second injection. Pleural fluid and blood were obtained just before (0 h) and 9, 24, 48, and 72 h after the second injection. We found the anion gap correlated with pH, the glucose, protein, and lactate dehydrogenase levels, pleural-fluid/plasma protein and lactate dehydrogenase ratios, and WBC count (all p < 0.001). The pH and protein ratio together accounted for 95% of all anion gap variation within individual subjects. We also found the influence of the PCO2 level on pH was not significant after taking into account the influence of the anion gap. These results suggest the anion gap may be useful in the clinical evaluation of pleural effusions and could potentially replace the pH measurement.

Concentration of tumor-associated trypsin inhibitor (TATI) in pleural effusions

We measured the concentration of tumor-associated trypsin inhibitor (TATI) in plasma and pleural fluid of 84 patients with pleural effusions of various causes. We observed elevated (greater than 30 micrograms/L) TATI levels in pleural fluid in 45 percent of patients with pleural effusion associated with malignant disease and in 15 percent of patients with benign disease. Similar results were obtained for TATI in plasma. The concentration of TATI in pleural fluid closely parallelled that in plasma. In patients with renal insufficiency and in patients with biliary obstruction, the TATI levels were elevated both in plasma and pleural fluid. A positive correlation was seen between the concentration of TATI and the activity of alkaline phosphatase in plasma. The results show that simultaneous determination of TATI in plasma and pleural fluid improves the diagnosis of cancer only marginally. Our results also support the hypothesis that elevated TATI levels may reflect an acute phase reaction caused by inflammatory disease or tissue destruction associated with cancer not only in inflammatory conditions, but also in malignant disease where the tumor itself is not producing TATI.

Neutrophil elastase alpha 1-proteinase inhibitor complexes in pleural effusions

Polymorphonuclear (PMN) granulocyte derived neutrophil elastase (NE) is rapidly antagonized by alpha 1-proteinase inhibitor (alpha 1 PI) in vivo. To determine the clinical value of elastase alpha 1-proteinase inhibitor complexes (E-alpha 1 PI) in pleural effusions, fluid samples of 99 patients were examined. Fifty-six had malignant effusions, 30 had non-malignant exudates (pleural protein above 3 g/dl) mainly of inflammatory origin, and 13 patients had low protein transudates (below 3 g/dl) due to congestive heart failure. Nonmalignant exudates showed significantly higher (P less than 0.001) concentrations of E-alpha 1 PI compared with malignant effusions or low protein transudates (P less than 0.001). Malignant exudates secondary to lung cancer were characterized by higher (P less than 0.001) median pleural E-alpha 1 PI concentrations compared to malignant exudates due to primarily extrathoracic malignancies. Total pleural leukocyte counts and pleural neutrophil counts were performed in 68 effusions. By this means no clear-cut differentiation between malignant and nonmalignant exudates seems possible except for marked empyema. In conclusion, E-alpha 1 PI complexes in pleural fluid may better reflect the stage of inflammation of pleural effusions rather than mere pleural leukocyte counts. Low levels of E-alpha 1 PI complexes (less than 75 ng/ml) in pleural exudates with protein values above 3 g/dl are characteristic of malignant exudates. Determination of E-alpha 1 PI in pleural exudates may serve as a sensitive marker of inflammation and useful adjunct to pleural cytology in aspects of differential diagnosis of pleural effusions.

Pleural fluid ferritin concentrations in human disease

The concentration of ferritin was measured in the pleural fluid of 108 patients with pleural effusions. In all groups of patients the ferritin concentration was higher in pleural fluid than in serum. The greatest differences, with up to 100 times more ferritin in the pleural fluid, were found for patients with rheumatoid pleurisy, malignant effusions, and empyema. In patients with non-malignant inflammatory pleural effusions the concentration of ferritin in pleural fluid correlated significantly with other pleural fluid indices of inflammation: there was a positive correlation with lactate dehydrogenase activity and a negative correlation with concentrations of glucose and complement components C3 and C4. Ferritin was detected immunocytochemically only in the macrophages found among the pleural fluid cells. Our study shows that large amounts of ferritin accumulate locally in the pleural cavity in certain types of pleural inflammation. The accumulation is probably partly the result of increased local reticuloendothelial system activity. Determination of the concentration of ferritin in pleural fluid may provide corroborative information for differential diagnosis and may further our understanding of the pathogenetic events that lead to the perpetuation of inflammatory activity in pleural effusions.

Thoracoscopic, histological, and clinical findings in nine case of rheumatoid pleural effusion

A characteristic thoracoscopic picture of a granular parietal pleural surface was found in nine patients with rheumatoid pleurisy. Characteristic changes could be identified histopathologically in material obtained by biopsy. The rheumatoid pleural effusion resolved within an average of 14 months and no serious complications developed after the pleurisy. It is concluded that in rheumatoid pleural effusion a positive diagnosis can be made by thoracoscopy, preferably supported by the identification of microscopic structural changes in the parietal pleura.