The blood F VIII:Ag/F VIII:C ratio as an early indicator of deep venous thrombosis during post-traumatic immobilization.

Twenty-two consecutive patients with spinal fractures (eight with spinal cord injuries) were studied. All patients were immobilized in bed for 6 weeks after trauma. The occurrence of deep venous thrombosis (DVT) was detected by the 125I-labeled fibrinogen test and confirmed by venography. F VIII:C, F VIII:Ag, and AT III activities were determined 2, 6, and 10 to 12 days after trauma. All paralyzed patients (n = 8) developed DVT and two of them had pulmonary embolism within 5 days after trauma. F VIII:Ag and F VIII:C disproportionally increased and the values of F VIII:Ag/F VIII:C ratio above 2 predicted DVT. AT III remained normal during the whole immobilization time and the values of DVT(+) and DVT(-) groups were comparable.