PAI-1 Level Differences in Malignant Plural Effusion, Parapneumonic Pleuritis, and Cardiac Hydrothorax

Background and Objectives: Plasminogen activator inhibitor-1 (PAI-1) is a fibrinolytic system enzyme whose role in various fibrinolytic processes is currently unknown. In clinical manifestations of pleural liquids of diverse etiology, various levels of fibrinolytic activity can be observed—parapneumonic processes tend to loculate in fibrin septa, while malignant pleural effusion (MPE) does not. The purpose of this study was to determine possible differences in PAI-1 levels in pleural effusions of varied etiology. Material and Methods: PAI-1 level in pleural effusion and serum was determined in 144 patients with pleural effusions of various etiology (cardiac hydrothorax—42 patients (29.2%), MPE—67 patients (46.5%), parapneumonic pleuritis—27 (18.8%), tuberculous pleuritis—6 patients (4.1%), pancreatogenic pleuritis—1 patient (0.7%) and pulmonary artery thromboembolism with pleuritis—1 patient (0.7%)). 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. However, there was no statistically significant difference between PAI-1 levels in the pleural effusion and serum in the cardiac hydrothorax and MPE groups. Conclusion: The PAI-1 level in MPE and cardiac hydrothorax was statistically significantly lower than in parapneumonic pleuritis.