Fibrinogen, fibrin(ogen) degradation products and fibrinopeptide A in pleural effusions. High turnover of fibrinogen in pleurisy.

Fibrinogen, fibrin(ogen) degradation products (FDP) and fibrinopeptide A (FPA) were analysed in pleural fluids from 20 consecutive patients with major effusions of various aetiology. FPA is a short-lived polypeptide which is split off from fibrinogen, whereafter fibrin is formed. FDP are formed through lysis of fibrin or fibrinogen. In 18 patients no fibrinogen could be detected in pleural fluid, whereas two (both having malignant tumours) had detectable but low concentrations. High FPA concentrations, interpreted as reflecting very recent fibrin formation, were found in all pleural fluids except for one case of empyema and one transudate. Plasma concentrations were low in most cases. The same pattern was found with regard to FDP, i.e. exudates showed high concentrations, whereas plasma concentrations were low. The only patient with a transudate showed absence of fibrinogen and low concentrations of FDP and FPA. We interpret our findings as indicative of a high rate of fibrin formation and degradation in pleural exudates and have not found any differences between various types of pleural exudates. Consequently, the findings may illustrate the close association between the coagulation system and inflammatory reactions which may be common to most pleural diseases.