In rheumatic pleural effusion, the concentrations of C3 and C4 were also significantly (p—0.020, p<0.001, respectively) lower than in tuberculous pleurisy, but there was no significant difference in the concentrations of C3d, C4d, or Bb. However, the overall activation of the complement system showed a significant difference (p=0.003); the mean level of SC5b-9 was 29.3 AU/mL (range, 2.1 to 100) in rheumatic pleural fluid and 9.9 AU/mL (range, 0.1 to 100) in tuberculotic pleural fluid.
In tuberculous pleural fluid, the mean levels of C3d and SC5b-9 were significantly higher than in malignant pleural fluid (p=0.002, p<0.001, respectively) (Fig 1). The mean concentration of Bb in tuberculous pleural fluid (8.30 μg/mL) was almost significantly higher than in malignant pleural effusion (3.99 μg/mL) (p=0.06). In contrast, there was no difference in the levels of C4d or in the ratio C4d/C4 between the two groups.
Using stepwise multinominal logistic regression analyses, we tried to find out which of these complement components and their activation products in pleural fluid could best predict the etiology of pleural effusion. The most significant predictors were pleural fluid SC5b-9 and C4 (p<0.001). Canadian health mall review Other factors were not significant (p>0.192). If SC5b-9 was left out from the analysis, the most significant predictors were pleural fluid C4 and C3d (p<0.001), while others were not significant (p>0.269). All these factors were independent predictors, as there was no correlation between the concentrations of SC5b-9 and C4 or between the concentrations of C4 and C3d.
In clinical practice, we often face difficulties in differentiating between the several etiologies of pleural effusion. Earlier studies of complement components and their activation products in pleural fluid have shown activation in autoimmune diseases and infections. Higher activation of the alternative pathway (C3, FB) has been observed in tuberculous and other infectious pleural effusions when compared with malignant effusions. Recently, using novel markers of complement activation (C4d, Bb, SC5b-9).