Anti-Xa factor as a predictor of postoperative deep vein thrombosis in general surgery.

This study was stimulated by a recent report linking a low preoperative level of an endogenous coagulation inhibitor (anti-Xa factor) with an increased incidence of postoperative deep venous thrombosis (DVT) (Stamatakis et al., 1977). Preoperative and postoperative levels of anti-Xa were measured and correlated with the postoperative incidence of deep venous thrombosis assessed by the 125I fibrinogen uptake test to determine whether a high risk group could be isolated and a suitable regimen of prophylaxis introduced. In this study of 22 surgical patients the postoperative DVT rate was 41 per cent. However, preoperative measurements of anti-Xa activity failed to show any statistically significant difference between those patients with DVT and the non-DVT groups. The findings do not support the use of anti-Xa levels as a preoperative predictor of postoperative DVT in the individual.