Hara et al confirmed earlier findings and showed that the soluble terminal-phase complement complex (SC5b-9) was the most effective way to differentiate between tuberculous and malignant pleural effusions. In the present study, we have used both these methods, and other additional markers, to find out whether the analysis of complement components and their activation products could help in differentiating among rheumatic, malignant, and tuberculous pleural effusion.
Our criteria for diagnosing the etiology of pleural effusion were mainly based on clinical grounds that might be criticized cfm-online-shop.com canadian family pharmacy online. All the patients underwent thoracentesis and pleural biopsies, however, and the pleural fluid was thoroughly analyzed, including the determination of protein, cell counts, cytology, tuberculosis smear and culture, and lactate dehydrogenase to exclude other possible reasons for pleural effusion. We also have quite a long follow-up until now and there is no evidence of other etiologies. The malignant pleural effusion group included both patients with proven malignant pleural effusion and patients with malignant disease whose pleural fluid was not proven malignant but was neither transudate nor infectious. In complement components and their activation products, there were no differences between these patients. The tuberculous group consisted of 11 patients with positive response to chemotherapy but no other evidence for tuberculosis and the diagnosis of rheumatic pleurisy was mainly made by excluding other etiologies for pleural effusion in patients with rheumatoid arthritis. If the three groups included patients with wrong diagnoses, the differences between the groups had probably been even more evident in more strictly selected patients.
Our results differ from those of Hara et al; low SC5b-9 was observed in malignant effusions and high SC5b-9 was found in some patients with tuberculous pleural effusion. The highest values, however, were observed in those with rheumatic pleural effusions. Our results suggest that pleural complement activation is frequently associated with exudative pleural effusions. There might be two explanations for complement accumulation in the pleural fluid in disease: either the components are synthesized locally in the pleural cavity or the affected pleura is more permeable than normal.