Plasma concentrations of cross linked
fibrin degradation products, a marker of intravascular
thrombosis and fibrinolysis, were measured in 495 patients with suspected
pulmonary embolism referred for ventilation-perfusion lung scanning to determine whether concentrations are increased in
pulmonary embolism and their potential use in diagnosis. Lung scans were described as normal (n = 66) or as showing a low (n = 292), indeterminate (n = 58), or high probability (n = 79) of
pulmonary embolism. There was a difference between the mean levels of cross linked
fibrin degradation products in each scan category: normal scans, 142 ng/ml; low probability scans, 295 ng/ml; indeterminate probability scans, 510 ng/ml; high probability scans, 952 ng/ml (p less than 0.001). Of the patients with high probability scans, 96% had raised concentrations. Explanations for discrepant low results include incorrect scan diagnosis, delay in blood sampling, and anticoagulation. Of the patients with a low or indeterminate probability of
pulmonary embolism, 43% had increased concentrations of cross linked
fibrin degradation products that could be attributed in most cases to another illness. Owing to the wide range of values in each lung scan diagnostic category, raised concentrations of these
fibrin degradation products cannot be used without reference to the patient's clinical state as a discriminatory test for
pulmonary embolism. Further evaluation of the significance of normal concentrations in excluding a diagnosis of
pulmonary embolism appears to be warranted.