Calprotectin: a novel biomarker for the diagnosis of pleural effusion.

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.

On the identification of biomarkers for non-small cell lung cancer in serum and pleural effusion.

The current imperative need for new biomarkers of non-small cell lung cancer (NSCLC) prompted us to compare the proteome of serum and pleural effusion samples from cancer patients with those with benign lung diseases as pneumonia or tuberculosis. Samples were prefractionated through affinity chromatography prior to 2D-DIGE to detect proteins with altered expression in cancer patients. Overall, we identified more potential biomarkers in pleural effusion, which is closer to the affected organ, than in serum. Nevertheless, in both cases principal component analysis demonstrated that the pattern of significantly altered proteins discriminates between disease groups. The biomarker candidates comprise proteins increased in malignant pleural effusions as gelsolin and the metalloproteinase inhibitor 2, and others with lower levels as S100-A8 and S100-A9. The most interesting protein was the pigment epithelium-derived factor (PEDF), which is related to angiogenesis inhibition, and was significantly overexpressed both in serum and pleural effusion from NSCLC patients. More than 12 PEDF isoforms were specifically immunodetected in both fluids in 2-D blots, most of them overexpressed in NSCLC. Thus, further validation would be ideally directed to quantify individual PEDF isoforms, as it may be only one or some of them the ones altered in the cancer process.