In earlier studies, concentrations of C3d, C4d, and Bb fragments in pleural fluid have been higher in patients with tuberculous pleurisy than in patients with malignant pleurisy. In our study, pleural fluid C3d was significantly and Bb was almost significantly higher in tuberculous pleurisy than in malignant pleural effusions, but no significant difference was seen in the concentrations of C4d. Also, the ratio between C4d and C4 was in the same range in both groups. Humoral immunity has a minor role in tuberculous pleurisy. This fits well with negative classic pathway activation. Since the role of cell-mediated immunity in tuberculous pleurisy is well known, this finding provides evidence for alternative activation, but not for classic activation of the complement in association with the activated cellular immunity in this disease.
On the basis of the present study, malignant and rheumatic pleural effusion can reliably be differentiated according to the concentration of pleural fluid SC5b-9, whereas differentiating tuberculous and rheumatic pleurisy is more difficult, but still possible. Buy allegra online further Low levels of pleural fluid C3 and C4 together with high pleural and plasma SC5b-9 and high plasma Cls-Clr-CHNH refer to rheumatic rather than tu-berculotic origin.
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 effusions was also significantly higher than in tuberculous pleurisy, but some patients with tuberculous pleurisy had values of higher than 2 AU/mL. The concentrations of pleural fluid C3 and C4 were significantly lower in patients with rheumatic disease compared with patients with tuberculous or malignant pleurisy. The most significant predictors for etiology of pleural fluid were SC5b-9 and C4. Malignant and rheumatic pleural effusion can reliably be differentiated according to the concentration of pleural fluid SC5b-9, while differentiating tuberculous and rheumatic pleurisy is more difficult, though still possible. These observations suggest that the determination of complement components and their activation products in pleural fluid presents a new promising approach to differentiating rheumatic, tuberculous, and malignant effusions and should therefore be included in the assessment of pleural fluid when traditional diagnostic methods fail.