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.