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Background:Novel non-invasive biomarkers for the precise diagnosis of malignancy in pleural effusion (PE) are needed. The aim of this study was to determine the diagnostic accuracy of calprotectin for predicting malignancy in patients with exudative PE.Methods:Calprotectin concentration was measured in 156 individuals diagnosed with exudative PE (67 malignant and 89 benign). Calprotectin accuracy for discriminating between malignant and benign PE was evaluated using receiver operating characteristic (ROC) curves. Univariate and multivariate logistic regression were performed to test the association between calprotectin levels and malignant PE.Results:Calprotectin levels were significantly lower in malignant pleural fluid (257.2 ng ml−1, range: 90.7–736.4) than benign effusions (2627.1 ng ml−1, range: 21–9530.1). The area under the curve was 0.963. A cutoff point of ⩽736.4 ng ml−1 rendered a sensitivity of 100%, with a specificity of 83.15%, which could prove useful to delimit those patients with negative cytology tests that should be referred for more invasive diagnostic procedures. Logistic regression demonstrated a strong association between calprotectin and malignancy (adjusted OR 663.14).Conclusion:Calprotectin predicts malignancy in pleural fluid with high accuracy and could be a good complement to cytological methods.

In this study, we measured ADA and DPP-IV enzymatic activity and sCD26 concentration in 150 pleural effusion (PE) samples and tested for correlations between these and other cellular and biochemical measures. We found that DPP-IV in particular might improve the specificity (but not the sensitivity) of the ADA test for diagnosis of pulmonary tuberculosis, since half of the false ADA positive results in non-tuberculous PE were also DPP-IV positive. A percentage of patients with malignant PE were sCD26 or DPP-IV positive; however, some patients with benign PE also tested positive. As a pattern associated with DPP-IV (but not the CD26 protein) was observed in PE, we searched for a finding that might increase the value of these biomarkers for diagnosis of malignancy. The observed pattern was related to the presence of leukocytes, as indicated by correlations with the cell count, and to a band of 180 kDa, detected by immunoblotting.

Normal pleural fluid in humans is thought to have a low protein concentration, but in disease states where fluid accumulates into the pleural space, the protein profile may change dramatically. In the near future, research on such altered fluid proteome may give diagnostic and prognostic information or even predict therapeutic responses. Onedimensional, two-dimensional, differential gel electrophoresis as well as mass spectrometry have become the most important techniques for identifying disease-related proteins among various pleural pathologies. However, to date very few studies have applied proteomic technology to pleural fluids with the aim of discovering reliable and specific disease biomarkers.

Anti-tumor properties assigned to PEDF, beside its role as an inhibitor of angiogenesis, make it a promising candidate in the search of new biomarkers for malignancy. In this study levels of PEDF were investigated in pleural effusions from lung adenocarcinoma and benign inflammatory disease patients. The mean PEDF concentration in the malignant group was slightly superior to that in patients suffering benign diseases (4.59 μg/mL vs 3.97 μg/mL), although the difference did not reach statistical significance (P 0.166). Pleural effusion PEDF levels were not related to gender, age, smoking habit or pleural effusion size. We also investigated the possible relationship of PEDF levels in pleural effusion regarding clinicopathological features. Correlations were found for monocytes (P 0.010) and polymorphonuclear leukocytes (P 0.023) with PEDF levels in pleural effusion of malignant origin.