KL-6 and surfactant protein-D (SP-D) are pneumoproteins secreted mainly by type II pneumocytes in the lungs. It is plausible that these proteins may be secreted into the pleural cavity in case of pleural inflammation. In this study, we liked to explore the role of KL-6 and SP-D in aiding a diagnosis of pleural effusions.
Consecutive 157 patients with pleural effusions of unknown etiologies were included for this study. The effusion levels of KL-6 and SP-D were measured by enzyme-linked immunosorbent assay in 52 patients with malignant effusions, 33 patients with tuberculous (TB) pleurisy, 33 patients with parapneumonic effusions (PPE)/empyema and 39 patients with transudative pleural effusions.
The levels of effusion SP-D showed no significant difference among the four groups. In contrast, the median values of effusion KL-6 were highest in the malignant effusions, followed by TB effusions, PPE/empyema, and transudative effusions. The difference showed statistical significance p < 0.001). The cut-off value of effusion KL-6 selected using the receiver operating characteristic (ROC) curve to different malignant to benign effusions was 279.0 U/mL. The sensitivity and specificity of effusion KL-6 in aiding a diagnosis of malignant effusion were 63.5 % and 82.9 %, respectively. The sensitivity and specificity of effusion carcinoembryonic antigen (CEA) using the 6 ng/mL as the cut-off value were 67.5% and 88.3 %, respectively.
Our results indicated that effusion level of SP-D had no value in aiding a diagnosis of pleural effusion. In contrast, the level of KL-6 might be of considerable value in aiding a diagnosis of malignant effusion. Further studies with large population are needed to verify the role of KL-6 in serving as a marker for a diagnosis of malignant pleural effusion.
KL-6 may be a useful marker for aiding a diagnosis of malignant pleural effusion.
Hui-Hwa Tsai, No Financial Disclosure Information; No Product/Research Disclosure Information