Interleukin-6 and its relationships to acute phase proteins in serous effusion differentiation.

The aim of the study was to assess the discriminative power of cytokine interleukin 6 (IL-6) between transudative and exudative pleural and peritoneal effusions, and to compare IL-6 with common acute phase proteins in serous effusion differentiation. One hundred and forty-five consecutive patients with pleural or peritoneal effusion underwent diagnostic parecentesis. Patients were categorized in three groups. Malignant effusion (group A) 56 patients, non-malignant effusion (group B) 46 patients and transudate (group C) 43 patients. Serum and effusion levels of IL-6, C-reactive protein (CRP), alpha2-macroglobuline (alpha2-MG), alpha1-antitrypsin (alpha1-AT) and alpha1-acid glycoprotein (alpha1-AG) were determined. Serum IL-6 levels were significantly higher in groups A and B in comparison to group C (p<0.001 and 0.001, respectively). In addition, serum IL-6 levels were higher in group A compared to group B (p<0.001), while the studied acute phase proteins were not significantly different. All the studied parameters were higher in the effusions of groups A and B compared to group C. At a cut-off value of 72.1 fmol/ml IL-6 had a sensitivity of 82.6-89.3%, specificity of 88.4-90.7% and positive predictive value of 90.7-94.6% among the three groups. Our results suggest that IL-6 at levels > or =72.1 fmol/ml, alpha1-AT at > or =170 mg/dl and alpha1-AG at > or =52.3 mg/ml give strong evidences for malignancy in exudates.