SERPINE1 and Pleuritis: Results: The median PAI-1 level (ng/mL) was the highest in the parapneumonic pleuritis group both in the effusion and the serum, with values of 291 (213–499) ng/mL and 204 (151–412) ng/mL, respectively, resulting in a statistically significant difference (p < 0.001) from the cardiac hydrothorax and MPE groups.