Comparison Of 125-I Fibrinogen Kinetics And Fibrinopeptide A In Patients With Disseminated Neoplasias

To answer the question of whether and to what extent an elevated fibrinopeptide A (FPA) or an accelerated fibrinogen turnover reflect circulating thrombin action, the effect of heparin on FPA and on 125-I fibrinogen kinetics was studied in 15 patients with disseminated neoplasias. The plasma FPA levels were grossly elevated (4.6-20, mean 12.5 ng/ml) in 6 patients with evidence of thromboembolic disease or DIC, and moderately to grossly elevated (0.4-10.4, mean 4.8 ng/ml) in most of the other patients. The FPA fall found in 10/10 patients after heparin bolus suggested that plasma FPA were reflecting thrombin action on fibrinogen. However, in several cases the slew rate of FPA decrease was consistent with localized or extravascular, rather than with circulating thrombin action.

Although continuous heparin therapy normalized the FPA levels in 5 of the 6 treated patients, the acceleration of fibrinogen turnover was as important as in untreated patients (mean values in heparin treated and untreated patients: half-life t1/2: 2.85 vs 2.23 d, catabolic rate constant j₃: 0.40 vs 0.48 d^-1, turnover: 67.6 vs 70.2 mg/kg/d, respectively, with normal values of t1/2: 3.78-4.57 d, j₃: 0.22-0.33 d^-1, turnover 16.6-26.6 mg/kg/d). The comparison between data of the FPA-RIA and fibrinogen kinetics suggests that mechanisms other than thrombin-mediated fibrin formation substantially contributed to increase the fibrinogen turnover. It is concluded that the results of the FPA-RIA and of the 125-I fibrinogen kinetics have to be interpreted with caution in the diagnosis of low-grade or compensated intravascular coagulation.