Patients with persistent APC-resistance without factor V Leiden mutation

Background: Activated protein C (APC) resistance and factor V Leiden mutati on nle major risk factors for deep venous thrimbosis. Previous work has led to the view that the coagulation phenotype and the genetic defect are asso ciated in almost all patients. It has been reported about single APC-resist ent patients without associated factor V Leiden, but significance and throm botic risk of this constellation have not vet been established. Patients and methods: We tested 486 consecutive patients with deep venous t hrombosis, arterial disease or other than vascular disease for APC-resistan ce with a factor VIII based assay. Results: 149 patients (31%) showed a pathological APC-ratio. Sensitivity an d specificity for defection of factor V Leiden were 100% and 40%, respectiv ely At 6 months follow-up APC-ratio returned to normal in 55% of the patien ts with initial pathological APC-resistance. At 12 months follow-up 91% of the patients with persistent APC-resistance showed a pathological ratio as well. Conclusions: Patients with APC-resistance not due to factor V Leiden can be attributed to one subset with reversible APC-resistance - possibly due to a hyper-congulable state in an acute thrombotic situation, and to another w ith persistent APC-resistance.