Our differences can be explained by the following: (1) we measured PTX3 in serum rather than pleural fluid; (2) there were only 6 patients with parapneumonic effusions compared to 38 patients with pneumonia; and (3) we measured PTX3 at the time of admission in the early stages of pleural effusion and the results of their pleural fluid cultures were negative. This evidence concerns the gene PTX3 and Pleural effusion.